WHATWG Wiki - User contributions [en]

MetaExtensions

2011-01-16T14:43:40Z

Sbp: /* Proposals */ Alphabetically ordered, and added the BBC's "created" name.

This page lists the allowed extension values for the name="" attribute of the <meta> element in HTML5. You may add your own values to this list, which makes them legal HTML5 metadata names. We ask that you try to avoid redundancy; if someone has already defined a name that does roughly what you want, please reuse it.

== Registered Extensions ==

None so far. The spec defines five: [http://whatwg.org/specs/web-apps/current-work/#meta-application-name application-name], [http://dev.w3.org/html5/spec/Overview.html#meta-author author], [http://whatwg.org/specs/web-apps/current-work/#meta-description description], [http://whatwg.org/specs/web-apps/current-work/#meta-generator generator], and [http://dev.w3.org/html5/spec/Overview.html#meta-keywords keywords].

== Proposals ==

{|border=1 cellpadding=4 cellspacing=0
! Keyword
! Brief description
! Link to more details
! Synonyms
! Status

|-valign="top"
| audience
| To aid search engines in classifying and to aid directory compilers, an audience most appropriate for the page may be suggested. Subject matter may not be a good clue; for example, an analysis of children's literature may be directed to teachers. A value is free-form case-insensitive text without a comma. Multiple values are to be comma-separated. Singular and plural forms have the same meaning. Recognized values: -- "all" and "everyone", which have the same meaning -- "adult" and "mature" have the same meaning and are for content that only adults may access, but no one responsible for preventing a nonadult or the immature from accessing the page or its content should rely on either or both of these values to do so without other means (not the same as "grownup", which see) -- "child" and "juvenile", which have the same meaning -- "teen" -- "grownup" is not identical to "adult" or "mature" in not implying a precise boundary but is approximately any person who may be able to understand and apply the content (e.g., car driving instruction that may be read by a minor not yet old enough to drive a car but who would likely benefit from somewhat early exposure to the instruction) -- "parent" to include guardian and temporary caregiver -- "teacher" to include professor and ad hoc instructor -- "elementary school student" to include any student below high school -- "high school student" -- "elhi" to include any student in elementary school through high school -- "college student" including graduate and professional school -- "business" including management, finance, and prospective customers (this includes e-commerce and investor sites) -- "health" including any health care provider including alternative and ad hoc -- "patient" for any health care recipient -- "lawyer" including judge, paralegal, and jailhouse lawyer -- "law client" for any prospective recipient of a lawyer's service (not usually a social work client) with ''lawyer'' including paralegal and jailhouse lawyer but not necessarily judge -- "craft" for any craftworker including laborer and artisan -- "artist" including musician, actor, dancer, and sculptor and including creator and performer -- "military" including paramilitary -- "news" including any consumer of rapidly-developing news -- "introductory" and "beginner", which have the same meaning -- "intermediate" and "midlevel", which have the same meaning -- "advanced" and "advance", which have the same meaning -- "scholarly" and "scholar", which have the same meaning -- "popular" generally referring to a writing style -- "older" including retiree -- "institution" including from corporation to conspiracy (such as for management advice) -- "government" including agencies and prospective politicians -- values using any integer or single-digit decimal in the form of "grade 8" or "grade 6.4" including to refer to a reading comprehension level (this generally will not exceed 12 and might be meaningless above 20 so higher values may be interpreted as the highest meaningful value) -- "viewers" for when content (such as a movie) is intended almost entirely to be seen rather than read -- "listeners" for when content (such as music) is intended almost entirely to be heard rather than read but not generally including text-to-speech support -- "tts", "text-to-speech", or "text to speech", which three have the same meaning and which are for a page that has substantial support for TTS or that will be readily understood through TTS without need for such support (TTS is often aided by, e.g., pre-resolving pronunciation ambiguities in page coding) -- values using any numbers in the form of "3-6 years old", whether a range or a single-number value -- values using any decade in the form of "born in 1970s" Unrecognized values such as "botanists", "Texans", and "writers who use red ink" may be used but at a risk that a search engine or directory editor will either fail to recognize it or will interpret it in unpredictable ways, or will in the future. Spellings that are erroneous or slightly different from a recognized value may be interpreted by a search engine or directory editor as representing a recognized value. The absence of the keyword defaults to a value of "all" but without overriding another indication arrived at by other means.
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| Proposal

|-valign="top"
| bot-. . .
| Robot owners, to allow page authors access to robotic capabilities, e.g., to deny them, should prefix "bot-" to the name of their robot, especially for proprietary bots. Example: If a robot were to be named "dullbucklequiz", the name in the meta element would be "bot-dullbucklequiz". The value "bot-" alone represents all bots so prefixed, like a wildcard. Arguably, there's no need for a list here of any specific bots if http://user-agents.org or http://www.botsvsbrowsers.com/ (and perhaps other sites) is reliable.
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|-valign="top"
| created
| The datetime at which the document was created. The value is an ISO8601 date. The date MUST follow the [http://www.w3.org/TR/NOTE-datetime W3C Profile of ISO 8601] with a granularity of "Complete date:" or finer. The [http://www.bbc.co.uk/guidelines/futuremedia/desed/previousversions/searchmetadata_vs_1_0.shtml#metadata BBC] use this name.
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| Proposal

|-valign="top"
| creator
| Searching for one content creator's work requires a standard robot-parsable format for the information. A personal name, institutional name, or other text entry is permissible. One element represents only one creator. Multiple creators are to be represented with multiple tags. Search engines may index by any component of a name, so a content creator need only enter a name once in one first-last or family-given order (e.g., Pat Thunderbird or Thunderbird, Pat, but not requiring both).
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| Proposal

|-valign="top"
| datetime-coverage
| The author may be the best expert on which time frame is most relevant to the content. Leaving that to search engine analysis may be too chancy without search engine optimization, which analysis is difficult to apply by algorithm to, e.g., historical papers that may focus on the 1800s but mention 1731 and 1912 perhaps unimportantly. The value for this keyword is a date or time -- not a range and not vague, for which other keywords are proposed -- in a format in accordance with http://www.w3.org/TR/NOTE-datetime (albeit a note that's at W3C only for discussion). Any of the six levels of granularity in that note are acceptable, such as expressing only a year. Should this keyword appear more than once, all the values so appearing are determinative. Multiple values are to be expressed with separate meta elements lest the note be revised in the future in a way incompatible with comma-separating a list.
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|-valign="top"
| datetime-coverage-end
| This is identical to the keyword datetime-coverage except that it represents only the end. If this keyword is used without datetime-coverage-start (also proposed), its value is interpreted as ending a range without a start. Should this keyword appear more than once, all the values so appearing are determinative, in which case each represents the end of a different range assumed to be nonnesting. Example: If four elements happen to be in the order of datetime-coverage-end=1865, datetime-coverage-start=1914, datetime-coverage-end=1918, and datetime-coverage-start=1862, assuming proper formatting, the ranges should be interpreted as 1862-1865 and 1914-1918.
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| Proposal

|-valign="top"
| datetime-coverage-start
| This is identical to the keyword datetime-coverage except that it represents only the start. If this keyword is used without datetime-coverage-end (also proposed), its value is interpreted as starting a range without an end. Should this keyword appear more than once, all the values so appearing are determinative, in which case each represents the start of a different range assumed to be nonnesting. Example: If four elements happen to be in the order of datetime-coverage-start=1862, datetime-coverage-start=1914, datetime-coverage-end=1865, and datetime-coverage-end=1918, assuming proper formatting, the ranges should be interpreted as 1862-1865 and 1914-1918.
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|-valign="top"
| datetime-coverage-vague
| This is identical to the keyword datetime-coverage except that its value is not necessarily crisp. This keyword should be used only when datetime-coverage, datetime-coverage-start, and datetime-coverage-end are inappropriate, but there's no ban on using all four. Any text without a comma can be the value (e.g., Pleistocene, 1820s, Tuesdays, or before we were born); multiple values are comma-separated. If this keyword is used with datetime-coverage, datetime-coverage-start, or datetime-coverage-end, the vague value should be exploited along with the value/s for the other keyword/s. Should this keyword appear more than once, all are determinative.
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|-valign="top"
| DC.
| Dublin Core, maintained by Dublin Core MetaData Initiative (DCMI), is an extensive system with some overlap with non-DC names. This reserves all strings that begin with DC and a dot. ''Not true; DC-HTML doesn't use hardwired prefixes, but defines the prefixes using link/@rel="scheme.prefix"''
| [http://www.DublinCore.org DCMI]
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| Proposal

|-valign="top"
| dir-content-pointer
| When several pages in a directory include main content, a table of contents, an index, and the like, a search engine may be able to organize results more usefully by identifying which is which with a standard vocabulary, helpful when different publishers use different conventions when displaying or printing content. A value is free-form case-insensitive text without a comma and optionally with a trailing number. Multiple values are to be comma-separated (multiple values are appropriate when one document serves multiple purposes). Singular and plural forms have the same meaning. Recognized values, which are pointer types to which numbers may be suffixed, are limited to "start" meaning 'the first page that should be seen by a user' (this may be anywhere in the directory and anywhere within content), "toc" meaning 'table of contents', "intro" including introductions, forewords, prefaces, and tables of figures, "abstract", "main", "bibliography" and "biblio", which have the same meaning, "index" which may mean 'sitemap' or not, "afterword" and "update" which have the same meaning and need not actually update, "credit" meaning 'credits and acknowledgments', and "author bio" meaning 'author's biography', including any information about the author including credentials and contact information. The number suffix may be spaceless or not. When numbers are suffixed, a search engine or directory should arrange like items in numerical order in the results, with unnumbered items following like items that are numbered, e.g., intro 1, intro 2, main 1, main 2, main, main, and so on. Each directory and each subdirectory has its own sequence.
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|-valign="top"
|expires
|<code>meta name='expires'</code> defines the expiration date of the page. This can be used for web pages in preparation for an upcoming event, e.g. a registration form for an exposition or competition, or other cases with a pre-set date when the document will no longer be valid, e.g. a product offer in a special sale or a support page for a product known not to be supported anymore from a given time onward.

Search engines should respond to this meta tag in a reasonable way, i.e. by removing the page from their main search results after the expiration date (possibly still returning the result in a special search for expired pages as long as the page exists and is not explicitly excluded via <code>robots.txt</code> or <code>meta name='robots'</code> etc.) or simply by indicating to the user that this result is out-of-date.

The content attribute should define the expiration date in accordance with http://www.w3.org/TR/NOTE-datetime . The meta tag should not be used for pages without expiration date. However, for historical reasons, search engines should also interpret other date formats where possible and should be prepared to find values such as "", "0", "no" and "never". Such non-date values are to be interpreted as no expiration date.

Correctly formatted example:
<code><pre><meta name='expires' content='2012-12-31T23:59Z'></pre></code>

This tag is not to be confused with and has a different meaning than <code>meta http-equiv='expires'.</code>
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|-valign="top"
| format-print
| This is to allow a user agent to inform an operating system or a printer driver of the preferred print medium, such as the paper size. A value is free-form case-insensitive text without a comma. Multiple values are to be comma-separated (multiple values might be appropriate because standard paper sizes vary around the world). Singular and plural forms have the same meaning. Recognized values are limited to "letter", "A4", "legal", "A5", "B5", "monarch", "envelope 10" meaning size #10, "envelope 6-3-4" meaning size #6 3/4, values with integers and decimals in the form of "8.5 x 11" or "8.5x11" in which spacing of the "x" does not affect meaning, "paper", which means 'paper of the default color (usually white) and weight (usually 20-lb. stock)', "white", "yellow", "pink", "blue", "green", "violet", or "multicolor", which means a medium of the given color or mixed, "letterhead", "p2 letterhead" meaning 'letterhead intended for any page except the first', "watermark" meaning a 'special watermark such as an organization's own', and "plain" meaning 'not preprinted and not letterhead (it may have a paper manufacturer's watermark not related to letterhead)'. Omitting "paper" when another recognized value is given defaults to an implied meaning of 'paper' with the other value; e.g., "letter" means 'letter paper'; the same principle applies to a medium's color (the default being white for paper and colorless for transparency) and plainness or lack thereof (the default being plain). Other values should be proposed before being recognized here. Label sizes should be proposed here for labels that are not on backing sheets that fit one of the recognized values, e.g., labels on narrow rolls. Blueprint paper sizes should be proposed here. Media other than standard paper, such as onion skin, heavier paper, card, and clear or color transparency, should be proposed here. The user agent may, with the user's or user sysadmin's permission (as by a menu-driven default), interpret a value to offer an alternative the user might accept and software and firmware other than the UA may interpret a value to the same end with or without permission, so this keyword is only suggestive; e.g., "letter" may be interpreted as "A4". The absence of the keyword defaults to a value determined by other than the page, e.g., by the printer driver or the user agent.
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|-valign="top"
| geographic-coverage
| The author may be the best expert on the geographic relevance of the content. Leaving that to search engine analysis may be too chancy without search engine optimization, which analysis is difficult to apply by algorithm to, e.g., historical papers and epidemiological studies which may mention locales only once. Absence of the keyword defaults to a value of world (not universe), unless the search engine chooses to interpret the page or larger unit for some other value, probably based on other than just contact information given in the website. The value for this keyword is a semicolon-separated list of one or more place-values, the order of which do not matter. One place-value will use commas to separate, in order, an optional standard natural language symbol applicable to the place-value (when omitted the language applicable to the page will control), a place-class, one or more place-subclasses if any, and one or more place name parts (where, e.g., in "Cape Town, South Africa", "Cape Town" is a place name part but "Town" is not). Spaces after semicolons and commas are optional; spaces within place-values are present when required for each place-value (e.g., "Quezon City", not an invented "QuezonCity"). To distinguish names that might otherwise be too similar, place-classes, all lower-case and hyphenatably spaceless, include ''outer-space'', ''region'' (on Earth and crossing or larger than a nation, e.g., southern hemisphere, polar region, temperate zone, or Asia), ''intntl-water'' (an 'international water body'), ''intntl-agcy'' ('international agency' or 'international collection', e.g., all U.N. member nations), ''nation'', ''within-nation'' (limited to only one political level down from nation, e.g., state, province, territory, possession, city not included within other political units of a nation, or any comparable unit), ''city'' (including town, village, hamlet, and any comparable political unit below the level of ''within-nation''), ''addr'' (including address, full-length street, building, institution, and neighborhood without political boundaries), ''pol-unit'' (''pol'' abbreviating 'political') (e.g., a place of disputed nationhood), ''hist-pol-unit'' (''hist'' abbreviating 'historical') (e.g., the Roman Empire), ''feature'' (e.g., river), ''num'' (e.g., latitude and longitude or outer-space equivalent in numbers), and ''ethereal'' (including thealogical/theological, fictional including from modern popular entertainment, and ancient secular mythical, but not including that which is asserted to be a state of mind or existence but not a place, such as nirvana). (Example for one hypothetical page: name="geographic-coverage" content="region, sub-Saharan Africa; nation, Panama; city, Panama, Panama; within-nation, Sao Paulo, Brazil; city, Sao Paulo, Sao Paulo, Brazil; within-nation, Mississippi, United States of America; region, Middle East; region, Midwest, United States of America; hist-pol-unit, Northwest Territory, United States of America; feature, river, Indus; outer-space, Indus; ethereal, ultima Thule; ethereal, Heaven; ethereal, Flatland; ethereal, Valhalla; en-US, addr, Hotel Valhalla, Fredrikstad, Norway; es, nation, Espana" (Indus is both a river and a constellation, illustrating the need for place-classes)). Ambiguity of place-values should be avoided despite convenience in coding because search engines may each interpret them as they see fit, e.g., it would be hard for an engine to distinguish New York from New York. For consistency of spelling, several authority lists should be settled upon, with legal, well-known, and disputed names and common abbreviations all being acceptable; but I'm not proposing one here now (relying on IANA's ccTLD list might be too complex to implement and still assure coding consistency, e.g., occasionally ccTLDs can be phased out and off of IANA's list) (a standard vocabulary possibly usable here is the [http://www.getty.edu/research/conducting_research/vocabularies/tgn/index.html Getty Thesaurus of Geographic Names Online], subject to licensing and charset choice); and promulgating authority lists may best be done publicly by search engine managements, who may disagree with each other. Allowing Unicode for non-Roman alphabet-using locales is desirable, but at present that may raise technical problems, including computer security issues, that are not yet readily soluble.
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|-valign="top"
| googlebot slurp msnbot Baiduspider ia_archive TEOMA twiceler
| These names are claimed by Google, Yahoo, Bing (Microsoft), Baidu (apparently), Alexa (used also by Wayback Machine), Teoma, and Cuil, respectively, for their robots, so I'm proposing them here because we should register meta name values claimed essentially proprietarily. For Baidu, the name is from third-party sources since Baidu.com's site is in Chinese. For TEOMA, case is in the original. E.g., <meta name="googlebot" content="noindex">; <META NAME="Slurp" CONTENT="NOODP"> (case in original); <META NAME="msnbot" CONTENT="NOODP"> (case in original); <META NAME = "TEOMA" CONTENT = "NOARCHIVE" > (case in original).
| [http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=93710 Google example] & [http://help.yahoo.com/l/au/yahoo7/search/indexing/indexing-11.html Yahoo example], both as accessed 4-28-09; [http://help.live.com/help.aspx?mkt=en-us&project=wl_webmasters Microsoft example], as accessed 4-27-09; [http://www.alexa.com/help/webmasters Alexa] & [http://www.archive.org/about/faqs.php Wayback Machine], both as accessed 9-19-09; [http://about.ask.com/en/docs/about/webmasters.shtml Ask example], as accessed 4-27-09; [http://www.cuil.com/info/webmaster_info/ Cuil], as accessed 9-19-09
| Slurp MSNBot
| Proposal

|-valign="top"
| keywords-not
| A comma-separated list of negative keywords that distinguish a closely-related theme from this page's true theme, to support Boolean NOT searches often more realistically than visible text can, especially when both themes share the same lexicon. If keywords is no longer a supported name for a meta element, keywords-not is superfluous; however, debate has been revived on whether keywords should be supported or not; see the keywords entry in this Wiki.
| [http://www.w3.org/Bugs/Public/show_bug.cgi?id=6609 W3C Bug 6609]
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|-valign="top"
| MSSmartTagsPreventParsing
| Microsoft introduced into Internet Explorer 6 Beta a feature that some website designers wished to preclude from applying in order to prevent public misunderstanding of their websites. The feature allowed a browser to add information but at a risk that users wouldn't know that it wasn't supplied by the website. This keyword was provided by Microsoft for those of us who wanted it. Its value was "TRUE". Microsoft spelled the keyword with some capitals and the value in all capitals but whether capitalization was required for either is unknown; some opinions vary. Since it need be understood by only one browser, and that one a beta version, full standards compliance should not be assumed, and original case may be required. (This tag is used by Google: "<meta content='true' name='MSSmartTagsPreventParsing'/>" appeared (with internal quote marks as singles) in the source code for <http://googleblog.blogspot.com/2009/04/listening-to-google-health-users.html>, as accessed 4-27-09.) Microsoft has apparently removed this instruction from its website on the ground that the beta version is no longer available and is not supported, but that doesn't assure that some users aren't still using the beta browser, perhaps inadvertently. Therefore, designers may wish to continue using the keyword and value and they are preserved here.
| e.g., [http://www.theregister.co.uk/2001/06/25/web_sites_banish_those_winxp/ The Register (U.K.)], [http://cc.uoregon.edu/cnews/summer2001/summer2001.pdf Univ. Oregon (U.S.) (PDF p. 18)], & [http://trillian.mit.edu/~jc/demo/SmartTagsOff.html John Chambers (U.S.) (job résumé near root)], all as accessed 4-19-09
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|-valign="top"
| page-datetime
| Better ranking in search engine results for recency or relevance to an event date would be aided by a standard format robots can parse. Users would save search time by not having to load many pages to find which ones are new or date-relevant. To supply a consistent and known format, the value for this keyword is a date-time expression formed in accordance with http://www.w3.org/TR/NOTE-datetime (albeit a note that's at W3C only for discussion). Any of the six levels of granularity in that note are acceptable, such as expressing only a year. Should this keyword appear more than once, only the first one so appearing is determinative.
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|-valign="top"
| page-version
| Pages may be revised several times daily. While date-time given to a granularity of a fraction of a second would often suffice, when a page has to be approved more than once before posting, any or no such time may be correct (without this keyword, a comment could be necessary but probably not parsable by an engine). In addition, versions regardless of date may show consecutiveness and can replace a date that must be vague. In that case, a version number may be more useful for searches and so a robot-parsable format is needed. The keyword's value is stated in ASCII digits, is any nonnegative base-10 rational number expressed as an integer or a decimal, with any number of decimal places allowed, and may be padded with any number of leading zeros to support extraction for ASCII sorting. Should this keyword appear more than once, only the first one so appearing is determinative. The versions 0 and 0.''n'', with ''n'' being to any number of places, signify beta versions, i.e., drafts, in the tradition of beta software, while versions 1 and higher ordinarily signify final-release versions. After a final-release version is released, a draft of a later version is not given a version number of 0 or 0.''n'', but is numbered higher than the last final-release version. It is suggested to page authors that draft status, if applicable, be shown in the visibly displayed text of the page, rather than that this meta tag be relied upon as the sole notice of draft status, as it may be inadequate notice if alone. To assign a low page-version such as 0.''n'' or 1, the page's URL, if static, may be used as the relevant premise. Thus, if a page is copied or moved to a new URL, the author may choose to restart page-version numbering from 0.''n'' or 1. If a page's URL is dynamic, e.g., if created on the fly from a script, the page author may prefer to use as the relevant premise for assigning a low page-version such as 0.''n'' or 1 the URL of the script or other technology that generates the dynamic-URL page, placing this meta element containing this attribute within the script or other technology, not within the generating page's head element (the generating page's head element may have its own meta element with this attribute describing the generating page). If one page containing the script or other technology that generates another page has more than one means for generating dynamic-URL pages, each means should contain its own meta element with this attribute. Page-version is thus largely independent of the page's date, although both would likely advance roughly in parallel.
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|-valign="top"
| publisher
| Searching for one content publisher's or page publisher's work requires a standard robot-parsable format for the information. This often differs from creator or author when the publisher is an institution. An institutional name, personal name, or other text entry is permissible. One element represents only one publisher. Multiple publishers are to be represented with multiple tags, although multiple publishers are less common than multiple authors or creators; multiplicity is more likely for a legal name and a well-known name. Search engines may index by any component of a name, so a publisher need only enter a name once in one order.
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|-valign="top"
| referrer
| Developers wish to control the sharing of referrer information with linked resources and followed links at the meta level. It's sometimes desirable to share referrer information from secure to non-secure resources. The proposal is to add:

<code><pre><meta name="referrer" content="never|default|always"></pre></code>

Where the value of the '''content''' attribute is:
* '''never''': No referrer information is leaked when following a links or requesting resources.
* '''default''': Include referrer information in non-secure context or for HTTPS resources with the same origin.
* '''always''': Include referrer information when following all links and requesting any resources.

Since <code><meta name="referrer" content="never"></code> is redundant with a proposed <code><link rel="nofollow"></code>, the <code><link rel="nofollow"></code> proposal should be supplanted with this one, which provides more robust control.
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|-valign="top"
| resolutions
| Authoring web sites to use resolution independent images that display beautifully on high-resolution displays should be made as easy as possible for developers and should not require JavaScript to accomplish.

To accomplish this, I propose a new HTML Meta Tag, <code>resolutions</code>, that can be used to specify that high-resolution versions of images linked to from the page are available and that the browser should use them in place of the lower-resolution default images if it detects that a user is using a high-resolution screen. The resolutions meta tag lists the device-pixel ratios supported by images in the page.

So, for example…

<code><pre><meta name="resolutions" content="2x"></pre></code>

… means that the developer is telling the browser that she has created 2x resolution images for the images linked to from the current page and named them with a @2x suffix.

To illustrate, if her image tag is as follows…

<code><pre><img src="/images/flower.jpg" alt="A flower"></pre></code>

… then she has two image files under /images: the low-resolution default (flower.jpg), and a higher-resolution (200%) version named flower@2x.jpg.

(This is the same naming convention already used by Apple in its Cocoa Touch framework for automatically loading in higher-resolution versions of images.)

Based on the meta tag, if the browser detects that the user is running at a <code>min-device-pixel-ratio</code> of 2.0, it will automatically ask for the 2x version of the image (flower@2x.jpg) instead of the default image as specified in the image tag.

Finally, so as not to flood external sites with high-resolution image requests, this functionality would only work for local images specified via relative links.

<h2>Multiple resolutions</h2>

The resolutions tag can also contain a list of supported device-pixel ratios so as to support even higher-resolution displays when and if they become available in the future.

For example:

<code><pre><meta name="resolutions" content="2x, 4x, 8x"></pre></code>

In this case, the developer would provide 2x, 4x, and 8x versions of all images. So, in the running example, she would make flower.jpg, flower@2x.jpg, flower@4x.jpg, and flower@8x.jpg.

<h2>Advantages</h2>

The advantages of this approach are several:

<ol>
<li>Makes it very simple for developers to support high-resolution displays like the iPhone 4's Retina screen</li>
<li>Does not require JavaScript</li>
<li>Does not change the default way that things work (if the meta tag is not specified, the browser simply behaves as it always has).</li>
</ol>

| [http://aralbalkan.com/3355 Proposal for native browser support of high-resolution image substitution]
[http://aralbalkan.com/3331 How to make your web content look stunning on the iPhone 4’s new Retina display]
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| Proposal

|-valign="top"
| rights
| As a page effectively appears in at least two forms, usually one as interpreted and displayed on a device and the other as source code, arguably intellectual property rights that must be asserted must be asserted in ways understandable in both contexts. For example, &copy; is a raw representation that may legally fail as part of copyright notice to someone seeing source code and not the display, important when someone wants to copy source code for use elsewhere and may rely on a defense of innocent infringement (at least in U.S.). While such assertions can be made in a comment element, it may be helpful to have a tag that search engines can parse and index verbatim. The value may include standard and nonstandard notices, invocations of licenses such as GFDL and ASCAP, and any other information. Content is defined as free-form, leaving the page author discretion for the entry. Statements in one tag may discuss several portions of the page differently, e.g., with different licenses. More than one license may be offered, along with the page's relationship to all. Not all statements need be license grants. A statement may state whom to ask for reprint permission or may reserve all rights, for example. Only one meta tag with this keyword may be present. Page authors must not use more than one. A UA finding multiple such tags on one page must ignore all of them. The copyright symbol that would be generated by its character entity is not recommended for legal notice in source code when the word 'Copyright' may be used instead, because the entity may be read in raw form, but use is up to the page author. The same concept applies to any intellectual property rights symbol for which a suitable alternative is available, such as for trademark or service mark. ASCII text would not suffice when a name or notice legally may have to be in a non-Roman alphabet, but no alternative may yet exist in HTML5. Search engine storage may impose a length limit, but, because of legal consequences, if the value's length exceeds a given limit the search index should retain or interpret none of it but only refer to it. The content string may only be copied verbatim in its full length, referred to, or ignored. It may not be, for example, paraphrased, truncated, interpreted, or classified except in addition to being copied verbatim in its full length. Ignoring shall not void, nullify, or alter any rights stated in such tag. For the synonymy, ''IP'', ''IP-rights'', and ''IP-right'' are not reserved; while the abbreviation ''IP'' 'intellectual property' is common among attorneys in the U.S., page authors will more likely be computerate, and the abbreviation may be wanted for 'Internet Protocol'.
| [[Talk:MetaExtensions#rights:_why_reversion|Talk]]
|
| Proposal

|-valign="top"
| rights-standard
| The purpose is to enable search engines and other cataloging services to compile the types of rights allocated to the work.

Format:
<pre><meta name="rights-standard" content="type;rights" /></pre>

The following are case-insensitive, except object ID.

* type - item these rights apply to
** (null) - everything; trailing semicolon is not included in this case
** code - the HTML code (and embedded other?) of the page.
** content - the entire content of the page
** object - a specific object, (for example, an image).
*** format is "object;" followed by the object ID; e.g., <code>object;left_middle-column</code>
* rights - what rights are assigned to the item
** "coprYYYY" -- work is copyrighted as of YYYY year
** "CC:" - Creative Commons; followed by any number (in any order) of additional attributes:
*** "BY" - By Attribution
*** "SA" - Share Alike
*** "ND" - No Derivatives
*** "NC" - No Commercial
** "PD" - Public domain

Examples:

* Page content is CC By Attribution
<meta name='rights-standard' content='content;cc:by' />

* Page code is CC By Attribution, Share alike
<meta name='rights-standard' content='code;cc:bysa' />

* Object with ID "item_1" is CC By Attribution, no derivatives, no commercial; object with ID "item_2" is public domain.
<meta name='rights-standard' content='object;item_1;cc:byndnc' />
<meta name='rights-standard' content='object;item_2;pd' />

* Everything on the page is copyrighted
<meta name='rights-standard' content='copr2009' />

| [[Talk:MetaExtensions#rights:_why_reversion]]

[http://creativecommons.org/about/licenses Creative Commons types and attributes]
|
| Proposal

|-valign="top"
| robots
| A comma-separated list of operators explaining how search engine crawlers should treat the content. Possible values are "noarchive" to prevent cached versions, "noindex" to prevent indexing, and "nofollow" works as the link rel value with the same name. This meta name is already supported by every popular search engine. The content value "NOODP" has been offered elsewhere, so I'm proposing it here. It blocks robots from using [http://www.dmoz.org Open Directory Project] descriptions of a website instead of Web pages' own meta descriptions. It may have been introduced by Microsoft. The content value "NOYDIR" has been offered by Yahoo, so I'm proposing it here. It blocks Yahoo's robot from using the Yahoo directory's descriptions of a website instead of Web pages' own meta descriptions. Whether any other robot supports this is unknown but possibly no other search engine uses Yahoo's directory anyway.
| [http://www.robotstxt.org/wc/exclusion.html#meta Robots exclusion protocol], [http://www.google.com/support/webmasters/bin/answer.py?answer=61050 Googlebot], [http://help.yahoo.com/help/us/ysearch/slurp/index.html Yahoo! Slurp], and [http://about.ask.com/en/docs/about/webmasters.shtml Ask.com Teoma]; NOODP value: [http://www.google.com/support/webmasters/bin/answer.py?hl=en&answer=35264 Google], [http://help.yahoo.com/l/us/yahoo/search/indexing/indexing-11.html Yahoo], & [http://help.live.com/help.aspx?mkt=en-us&project=wl_webmasters#faq38 Microsoft (click "How does Live Search generate a description of my website?")], all as accessed 4-28-09; NOYDIR value: [http://ysearchblog.com/2007/02/28/yahoo-search-support-for-noydir-meta-tags-and-weather-update/ Yahoo], as accessed 4-28-09
|
| Proposal

|-valign="top"
| subj-. . .
| To classify by subject a page's content, a standard subject taxonomy that will be recognized by a search engine or directory will help. Because many such high-quality taxonomies exist, only a prefix is proposed. Over time, particular taxonomies, in print or online, may be recognized here and keywords assigned for each. The keyword will be constructed case-insensitively with subkeywords in the form subj-[nationAbbrev]-[taxonomy]-[edition][-optionalSubedition], e.g., subj-US-MeSH-2009online (perhaps). After "subj-", the second subkeyword will identify the nation where the taxonomy is published or offered as an aid in identifying the taxonomy and does not limit the subject coverage; e.g., a taxonomy published in Japan may be ideal for classifying Canadian botany or Peruvian economy. As subject values may vary between editions of one taxonomy, an edition and optionally a subedition is to be identified in the third and optionally the fourth subkeywords. The subedition, if any, is any update or revision occurring between editions, such that a value drawn from that edition and subedition is stable. The means of identifying edition and subedition should be included in the registration of a keyword. Examples of taxonomies from the U.S. include MeSH (medical) and the Library of Congress Subject Headings. The value identifying a subject for a Web page will be drawn from the cited taxonomy's edition and subedition. If the value should have a style to prevent ambiguity in interpretation, that style is to be registered here for that keyword. Multiple values are expressed with multiple meta elements, one value for each, since comma-separation is probably not compatible with all taxonomies. If a value requires case-sensitivity to prevent confusion, the entry here registering the keyword must accommodate that need with the needs of HTML 5 with an appropriate rule. To that end, a proposal to allow case-sensitivity in meta tags under some circumstances has been offered in the W3C bug reporting system.
| [http://www.w3.org/Bugs/Public/show_bug.cgi?id=6854 W3C Bug 6854]
| subject-. . .
| Proposal

|}

== Failed Proposals ==

{|border=1 cellpadding=4 cellspacing=0
! Keyword
! Brief description
! Link to more details
! Synonyms
! Status
|-valign="top"
| cache
| This doesn't actually work; use HTTP headers instead. Value must be "public", "private", or "no-cache". Intended as a simple way to tell user agents whether to store a copy of the document or not. An alternate for HTTP/1.1's cache-control; for publishers without access to modifying cache-control.
| none
|
| Unendorsed
|}

== Process ==

For the "Status" section to be changed to "Accepted", the proposed keyword must be defined by a W3C specification in the Candidate Recommendation or Recommendation state. If it fails to go through this process, it is "Unendorsed".

For more details, see [http://whatwg.org/specs/web-apps/current-work/#concept-meta-extensions the HTML5 specification].

FAQ

2009-05-23T12:01:25Z

Sbp: /* HTML5 should support a way for anyone to invent new elements! */ Updating to conform with the flavour of the month.

== The WHATWG ==

=== What is the WHATWG? ===

The WHATWG is a growing community of people interested in evolving the Web. It focuses primarily on the development of HTML and APIs needed for Web applications.

The WHATWG was founded by individuals of Apple, the Mozilla Foundation, and Opera Software in 2004, after a W3C workshop. Apple, Mozilla and Opera were becoming increasingly concerned about the W3C’s direction with XHTML, lack of interest in HTML and apparent disregard for the needs of real-world authors. So, in response, these organisations set out with a mission to address these concerns and the Web Hypertext Application Technology Working Group was born.

=== What does the acronym WHATWG stand for? ===

It stands for "Web Hypertext Application Technology Working Group".

=== What is the WHATWG working on? ===

The WHATWG is working on HTML 5 (see below). In the past it has worked on Web Forms 2.0 and Web Controls 1.0 as well. Web Forms 2.0 (see below) has reached a stable stage and we're awaiting implementation experience. Web Controls 1.0 has been abandoned for now, awaiting what [http://www.w3.org/TR/xbl/ XBL 2.0] will bring us.

=== How can I get involved? ===

There are lots of ways you can get involved, take a look and see ''[[What you can do]]''!

=== Is participation free? ===

Yes, everyone can contribute. There are no memberships fees involved, it's an open process. You may easily subscribe to the WHATWG [http://whatwg.org/mailing-list mailing lists]. You may also [http://blog.whatwg.org/w3c-restarts-html-effort join the the W3C's new HTMLWG] by going through the slightly longer application process.

== The WHATWG Process ==

=== How does the WHATWG work? ===

People send e-mail to [http://www.whatwg.org/mailing-list#specs the mailing list]. The editor then reads that [http://www.whatwg.org/issues/ feedback] and, taking it into account along with research, studies, and feedback from many other sources (blogs, forums, IRC, etc) makes language design decisions intended to address everyone's needs as well as possible while keeping the language consistent.

This continues, with people sending more feedback, until nobody is able to convince the editor to change the spec any more (e.g. because two people want opposite things, and the editor has considered all the information available and decided that one of the two proposals is the better one).

This is not a consensus-based approach -- there's no guarantee that everyone will be happy! There is also no voting.

There is a small oversight committee (known as the "WHATWG members", see the [http://www.whatwg.org/charter charter]) who have the authority to override or replace the editor if he starts making bad decisions.

Currently the editor is Ian Hickson.

=== How should tool developers, screen reader developers, browser vendors, search engine vendors, and other implementors interact with the WHATWG? ===

Feedback on a feature should be sent to whatwg@whatwg.org (but you have to [http://whatwg.org/mailing-list#specs join the mailing list] first), or ian@hixie.ch. All feedback will receive a reply in due course.

If you want feedback to be dealt with faster than "eventually", e.g. because you are about to work on that feature and need the spec to be updated to take into account all previous feedback, let the editor know by either e-mailing him (ian@hixie.ch), or contacting him on [[IRC]] (Hixie on Freenode). Requests for priority feedback handling are handled confidentially so other implementors won't know that you are working on that feature.

Questions and requests for clarifications should be asked either on the mailing list or on [[IRC]], in the #whatwg channel on Freenode.

=== When will HTML 5 be finished? ===

"Finished" is a big deal... You'll be able to use HTML5 long before then. See [[FAQ#When_will_we_be_able_to_start_using_these_new_features.3F|When will we be able to start using these new features?]]

It is estimated by the editor that HTML5 will reach the W3C Candidate Recommendation stage during 2012. That doesn't mean you can't start using it yet, though. Different parts of the specification are at different maturity levels. Some sections are already relatively stable and there are implementations that are already quite close to completion, and those features can be used today (e.g. <canvas>). But other sections are still being actively worked on and changed regularly, or not even written yet.

'''You can see annotations in the margins showing the estimated stability of each section.'''

The possible states are:

* ''Idea; yet to be specified'' -- the section is a placeholder.
* ''First draft'' -- An early stage.
* ''Working draft'' -- An early stage, but more mature than just "first draft".
* ''Last call for comments'' -- The section is nearly done, but there may be feedback still to be processed. Send feedback sooner rather than later, or it might be too late.
* ''Awaiting implementation feedback'' -- The section is basically done, but might change in response to feedback from implementors. Major changes are unlikely past this point unless it is found that the feature, as specified, really doesn't work well.
* ''Implemented and widely deployed'' -- the feature is specified and complete. Once a section is interoperably implemented, it’s quite stable and unlikely to change significantly. Any changes to such a section would most likely only be editorial in nature, particularly if the feature is already in widespread use.

There are also two special states:

* ''Being edited right now'' -- the section is in high flux and is actively being edited. Contact Hixie on [[IRC]] if you have immediate feedback.
* ''Being considered for removal'' -- for one reason or another, the section is being considered for removal. Send feedback soon to help with the decision.

The point to all this is that you shouldn’t place too much weight on the status of the specification as a whole. You need to consider the stability and maturity level of each section individually.

It is estimated, again by the editor, that HTML5 will reach a W3C recommendation in the year 2022 or later. This will be approximately 18-20 years of development, since beginning in mid-2004. That's actually not that crazy, though. Work on HTML4 started in the mid 90s, and HTML4 ''still'', more than ten years later, hasn't reached the level that we want to reach with HTML5. There is no real test suite, there are many parts of the spec that are lacking real implementations, there are big parts that aren't interoperable, and the spec has hundreds if not thousands of known errors that haven't been fixed. When HTML4 came out, REC meant something much less exciting than it does now.

For a spec to become a REC today, it requires two 100% complete and fully interoperable implementations, which is proven by each successfully passing literally thousands of test cases (20,000 tests for the whole spec would probably be a conservative estimate). When you consider how long it takes to write that many test cases and how long it takes to implement each feature, you’ll begin to understand why the time frame seems so long.

(In the interests of full disclosure, the W3C's [http://www.w3.org/2007/03/HTML-WG-charter.html#deliverables official line] is that the HTML5 spec will be complete, with interoperable implementations, in late 2010. However, that same timetable gave a date for First Public Working Draft that was eight months premature, and the W3C, as of the predicted date for the third milestone, Candidate Recommendation, had still not come anywhere near reaching the second milestone, Last Call. You can make your own judgements regarding the W3C timetable's credibility.)

=== Is there a process for removing bad ideas from the spec? ===

There are several processes by which we trim weeds from the specifications.

* On a regular basis, especially around explicit call-for-comments, we go through every section and mark areas as being considered for removal. This happened early in 2008 with the data templates, repetition blocks, and DFN-element cross references, for example. If no feedback is received to give us strong reasons to keep such features, then they eventually are removed altogether.

* Anyone can ask for a feature to be removed; such feedback is considered like all other feedback and is based on the merits of the arguments put forward.

* If browsers don't widely implement a feature, or if authors don't use a feature, or if the uses of the feature are inconsequential of fundamentally wrong or damaging, then, after due consideration, features will be removed.

Removing features is a critical part of spec development.

=== Is there a process for adding new features to the spec? ===

The process is rather informal, but basically boils down to this:
# Research the use cases and requirements by discussing the issue with authors and implementors.
# Come up with a clear description of the problem that needs to be solved.
# Discuss your proposal with authors and implementors. Read the responses. Listen to the feedback. Consider whether your ideas are good solutions to the use cases and requirements put forward. Discussions here should be done in public, e.g. on an archived public mailing list or documented in blogs.
# Get implementors to commit to implementing the feature. If you can't get several implementors to implement the feature, then get at least one user agent to implement it experimentally. Experimental implementations should be publicly available.
# Bring the experimental implementations to the attention of the spec's editor. Document the experience found from any implementations, the use cases and requirements that were found in the first step, the data that the design was based on.
# Demonstrate the importance of the problem. Demonstrate that the solution is one that will be used correctly and widely enough for it to solve the stated problem.
# Participate in the subsequent design discussions, considering all the proposals carefully. Typically at this step the original design gets thrown out and a significantly better design is developed, informed by the previous research, new research, and implementation and author experience with experimental implementations. Sometimes, the idea is abandoned at this stage.

If the idea survives the above design process, the spec will be eventually updated to reflect the new design. Implementations will then be updated to reflect the new design (if they aren't, that indicates the new design is not good, and it will be reworked or removed). The spec will be updated to fix the many problems discovered by authors and implementors, over a period of several years, as more authors and implementors are exposed to the design. Eventually, a number of provably interoperable implementations are deployed. At this point development of the feature is somewhat frozen.

Writing a comprehensive test suite is also an important step, which should start a bit before implementations start being written to the spec. (Test suites usually find as many problems with implementations as they do with the spec; they aren't just for finding browser bugs.) We don't yet have a good story with respect to test suites, sadly. If you want to help us out, let the mailing list know! Be aware, though, it's a lot of work.

== HTML5 ==

=== What is HTML 5? ===

[http://www.whatwg.org/specs/web-apps/current-work/ HTML 5] is the main focus of the WHATWG community and also that of the (new) W3C HTML Working Group. HTML 5 is a new version of HTML 4.01 and XHTML 1.0 addressing many of the issues of those specifications while at the same time enhancing (X)HTML to more adequately address Web applications. Besides defining a markup language that can be written in both HTML (HTML5) and XML (XHTML5) it also defines many APIs that form the basis of the Web architecture. These APIs are known to some as "DOM Level 0" and have never been documented. Yet they are extremely important for browser vendors to support existing Web content and for authors to be able to build Web applications.

=== What is Web Forms 2.0? ===

[http://www.whatwg.org/specs/web-forms/current-work/ Web Forms 2.0] is an update to the forms chapters of HTML 4.01 and XHTML 1.0. The specification is informally declared feature complete and the WHATWG is awaiting implementation experience. This specification will in due course be folded into the HTML 5 specification when HTML 5 reaches a more stable state.

=== How can I keep track of changes to the spec? ===

The specification is available in the [http://svn.whatwg.org/ subversion repository]. You may use any svn client to check out the latest version and use your clients diff tools in order compare revisions and see what has been changed. You may also use the online [http://html5.org/tools/web-apps-tracker (X)HTML5 Tracker Tool]. The tool provides an online interface for selecting and comparing revisions of the spec.

=== When will we be able to start using these new features? ===

As soon as browsers begin to support them. You do not need to wait till HTML5 becomes a recommendation, because that can’t happen until after the implementations are completely finished.

For example, the <canvas> feature is already widely implemented.

The specification has annotations in the margins showing what browsers implement each section.

=== What about Microsoft and Internet Explorer? ===

Microsoft has already started implementing parts of HTML5 in IE8.

HTML 5 is being developed with compatibility with existing browsers in mind, though (including IE). Support for many features can be simulated using JavaScript.

== Syntax issues ==

=== Will (X)HTML 5 finally put an end to the XHTML as <code>text/html</code> debate? ===

Yes. Unlike HTML 4.01 and XHTML 1.0, the choice of HTML or XHTML is solely dependent upon the choice of MIME type, rather than the DOCTYPE. See [[HTML vs. XHTML]]''

=== What will the DOCTYPE be? ===

In HTML:

<code><!DOCTYPE html></code>

In XHTML: no DOCTYPE is required and its use is generally unnecessary. However, you may use one if you want (see the following question). Note that the above is well-formed XML and so it may also appear in XHTML documents.

For compatibility with legacy producers designed for outputting HTML, but which are unable to easily output the above DOCTYPE, this alternative legacy-compat version may be used instead.

<code><!DOCTYPE html SYSTEM "about:legacy-compat"></code>.

Note that this is '''not''' intended for dealing with any compatibility issues with legacy browsers. It is meant for legacy authoring tools only.

Excluding the string <code>"about:legacy-compat"</code>, the DOCTYPE is case insensitive in HTML. In XHTML, it is case sensitive and must be either of the two variants given above. For this reason, the DOCTYPEs given above are recommended to be used over other case variants, such as <code><!DOCTYPE HTML></code> or <code><!doctype html></code>.

These alternatives were chosen because they meet the following criteria:

* They trigger standards mode in all current and all relevant legacy browsers.
* They are well-formed in XML and can appear in XHTML documents.
* It is possible to output at least one of the alternatives, if not both, with extant markup generators.
* They intentionally contain no language version identifier so the DOCTYPE will remain usable for all future revisions of HTML.
* The first is short and memorable to encourage its use.
* The legacy-compat DOCTYPE is intentionally unattractive and self descriptive of purpose to discourage unnecessary use.

=== Under what conditions should a DOCTYPE be used in XHTML? ===

Generally, the use of a DOCTYPE in XHTML is unnecessary. However, there are cases where inclusion of a DOCTYPE is a reasonable thing to do:

# The document is intended to be a polyglot document that may be served as both HTML or XHTML.
# You wish to declare entity references for use within the document. Note that most browsers only read the internal subset and do not retrieve external entities. (This is not compatible with HTML, and thus not suitable for polyglot documents.)
# You wish to use a custom DTD for DTD-based validation. But take note of [http://about.validator.nu/#faq what's wrong with DTDs].

=== How are pre-HTML5 documents parsed? ===

All documents with a text/html media type (that is, including those without or with an HTML 2.0, HTML 3.2, HTML 4.01, or XHTML 1.0 DOCTYPE) will be parsed using the same parser algorithm as defined by HTML5. This matches what Web browsers have done for HTML documents so far and keeps code complexity down. That in turn is good for security, maintainability, and in general keeping the amount of bugs down. The HTML syntax of HTML5 therefore does not require a new parser and documents with an HTML 4.01 DOCTYPE for example will be parsed using the HTML5 parser.

Validators are allowed to have different code paths for previous levels of HTML.

=== If there is no DTD, how can I validate my page? ===

With an [http://validator.whatwg.org/ HTML 5 validator].

=== What is an HTML Serialisation? ===

The HTML serialisation refers to the syntax of an HTML document defined in HTML5. The syntax is inspired by the SGML syntax from earlier versions of HTML, bits of XML (e.g. allowing a trailing slash on void elements, xmlns attributes), and reality of deployed content on the Web.

Any document whose MIME type is determined to be <code>text/html</code> is considered to be an HTML serialization and must be parsed using an HTML parser.

=== What is an XML (or XHTML) Serialisation? ===

The XML Serialization refers to the syntax defined by XML 1.0 and Namespaces in XML 1.0. A resource that has an XML MIME type, such as <code>application/xhtml+xml</code> or <code>application/xml</code>, is an XML document and if it uses elements in the HTML namespace, it contains XHTML. If the root element is “html” in the HTML namespace, the document is referred to as an XHTML document.

=== What MIME type does HTML5 use? ===

The HTML serialisation ''must'' be served using the <code>text/html</code> MIME type.

The XHTML serialisation ''must'' be served using an XML MIME type, such as <code>application/xhtml+xml</code> or <code>application/xml</code>. Unlike XHTML 1.0, XHTML 5 ''must not'' be served as <code>text/html</code>.

Using the incorrect MIME type (<code>text/html</code>) for XHTML will cause the document to be parsed according to parsing requirements for HTML. In other words, it will be treated as tag soup. Ensuring the use of an XML MIME type is the only way to ensure that browsers handle the document as XML.

=== Should I close empty elements with <code>/></code> or <code>></code>? ===

Void elements in HTML (e.g. the <code>br</code>, <code>img</code> and <code>input</code> elements) do not require a trailing slash. e.g. Instead of writing <code> </code>, you only need to write <code> </code>. This is the same as in HTML 4.01. However, due to the widespread attempts to use XHTML 1.0, there are a significant number of pages using the trailing slash. Because of this, the trailing slash syntax has been permitted on void elements in HTML in order to ease migration from XHTML 1.0 to HTML5.

HTML5 also introduces the ability to embed MathML elements. On elements inside a <code>math</code> element the trailing slash works just like it does in XML. I.e. it closes the element. This is only inside that context however, it does not work for normal HTML elements.

=== If I’m careful with the syntax I use in my HTML document, can I process it with an XML parser? ===

No, HTML and XML have [[HTML_vs._XHTML#Differences_Between_HTML_and_XHTML|many significant differences]], particularly parsing requirements, and you cannot process one using tools designed for the other. However, since HTML5 is defined in terms of the DOM, in most cases there are both HTML and XHTML serialisations available that can represent the same document. There are, however, a few differences explained later that make it impossible to represent some HTML documents accurately as XHTML and vice versa.

If you wish to process an HTML document as XHTML, it requires that you and convert it into XHTML first; and vice versa for processing XHTML as HTML.

=== What is the namespace declaration? ===

In XHTML, you are required to specify the [http://www.w3schools.com/xml/xml_namespaces.asp namespace.]

<html xmlns="http://www.w3.org/1999/xhtml">

In HTML, the <code>xmlns</code> attribute is currently allowed on any HTML element, but only if it has the value “<code>http://www.w3.org/1999/xhtml</code>“. It doesn’t do anything at all, it is merely allowed to ease migration from XHTML 1.0. It is not actually a namespace declaration in HTML, because HTML doesn’t yet support namespaces. See the question [[FAQ#Will_there_be_support_for_namespaces_in_HTML.3F|will there be support for namespaces in HTML]].

=== Will there be support for namespaces in HTML? ===

HTML5 is being defined in terms of the DOM and during parsing of a text/html all HTML elements will be automatically put in the HTML namespace, <code>http://www.w3.org/1999/xhtml</code>. However, unlike the XHTML serialization, there is no real namespace syntax available in the HTML serialization (see previous question). In other words, you do not need to declare the namespace in your HTML markup, as you do in XHTML. However, you are permitted to put an <code>xmlns</code> attribute on each HTML element as long as the namespace is <code>http://www.w3.org/1999/xhtml</code>.

In addition, the HTML syntax provides for a way to embed elements from MathML and SVG. Elements placed inside the container element <code>math</code> or <code>svg</code> will automatically be put in the MathML namespace or the SVG namespace, respectively, by the parser. Namespace syntax is not required, but again an <code>xmlns</code> attribute is allowed if its value is the right namespace.

In conclusion, while HTML5 does not allow the XML namespace syntax, there is a way to embed MathML and SVG and the xmlns attribute can be used on any element under the given constraints, in a way that is reasonably compatible on the DOM level.

=== How do I specify the character encoding? ===

For HTML, it is strongly recommended that you specify the encoding using the HTTP <code>Content-Type</code> header. If you are unable to [http://www.w3.org/International/O-HTTP-charset configure your server] to send the correct headers, then you may use the <code>meta</code> element:

<meta charset="UTF-8">

The following restrictions apply to character encoding declarations:

* The character encoding name given must be the name of the character encoding used to serialize the file.
* The value must be a [http://www.iana.org/assignments/character-sets valid character encoding name], and must be the preferred name for that encoding.
* The character encoding declaration must be serialized without the use of character references or character escapes of any kind.
* The <code>meta</code> element used for this purpose must occur within the first 512 bytes of the file. It is considered good practice for this to be the first child of the <code>head</code> element so that it is as close to the beginning of the file as possible.

Note that this <code>meta</code> element is different from HTML 4, though it is compatible with many browsers because of the way encoding detection has been implemented.

For polyglot documents, which may be served as either HTML or XHTML, you may also include that in XHTML documents, but only if the encoding is "UTF-8".

To ease transition from HTML 4 to HTML 5, although the former is the recommended syntax, you may also use the following. (This does not apply to XHTML or polyglot documents)

<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">

In XHTML, XML rules for determining the character encoding apply. The meta element is never used for determining the encoding of an XHTML document (although it may appear in UTF-8 encoded XHTML documents). You should use either the HTTP <code>Content-Type</code> header or the XML declaration to specify the encoding.

<?xml version="1.0" encoding="UTF-8"?>

Otherwise, you must use the default of <code>UTF-8</code> or <code>UTF-16</code>. It is recommended that you use <code>UTF-8</code>.

=== What are the differences between HTML and XHTML? ===

See the list of [[HTML vs. XHTML#Differences_Between_HTML_and_XHTML|differences between HTML and XHTML]] in the wiki.

=== What are best practices to be compatible with HTML DOM and XHTML DOM? ===

Though the intent is that HTML and XHTML can both produce identical DOMs, there still are some differences between working with an HTML DOM and an XHTML one.

Case sensitivity :
* Whenever possible, avoid testing Element.tagName and Node.nodeName (or do toLowerCase() before testing).
Namespaces:
* Use the namespace-aware version for creating elements: Document.createElementNS(ns, elementName)

=== Why does HTML5 legitimise tag soup? ===

Actually it doesn’t. This is a misconception that comes from the confusion between conformance requirements for documents, and the requirements for user agents.

Due to the fundamental design principle of supporting existing content, the spec must define how to handle all HTML, regardless of whether documents are conforming or not. Therefore, the spec defines (or will define) precisely how to handle and recover from erroneous markup, much of which would be considered tag soup.

For example, the spec defines algorithms for dealing with syntax errors such as incorrectly nested tags, which will ensure that a well structured DOM tree can be produced.

Defining that is essential for one day achieving interoperability between browsers and reducing the dependence upon reverse engineering each other.

However, the conformance requirements for authors are defined separately from the processing requirements. Just because browsers are required to handle erroneous content, it does not make such markup conforming.

For example, user agents will be required to support the marquee element, but authors must not use the marquee element in conforming documents.

It is important to make the distinction between the rules that apply to user agents and the rules that apply to authors for producing conforming documents. They are completely orthogonal.

== Feature proposals ==

=== HTML5 should support <code>href</code> on any element! ===

The spec allows <a> to contain blocks. It doesn't support putting href="" on any element, though.

Supporting <code>href</code> on any element has several problems associated with it that make it difficult to support in HTML5. The main reason this isn't in HTML5 is that browser vendors have reported that implementing it would be extremely complex. Browser vendors get to decide what they implement, and there's no point us telling them to do something they aren't going to do. In addition:

* It isn’t backwards compatible with existing browsers.
* It adds no new functionality that can’t already be achieved using the <code>a</code> element and a little script.
* It doesn’t make sense for all elements, such as interactive elements like <code>input</code> and <code>button</code>, where the use of href would interfere with their normal function.

The only advantage it seems to add is that it reduces typing for authors in some cases, but that is not a strong enough reason to support it in light of the other reasons.

Wrapping <a> elements around blocks solves most use cases. It doesn't handle making rows in tables into links, though; for those just do something like this instead:
<pre>
<tr onclick="location = this.getElementsByTagName('a')[0]"> ... </tr>
</pre>

=== HTML5 should support list headers! ===

You can give a header to a list using the <figure> and <legend> elements:

<pre>
<figure>
<legend>Apples</legend>
<ul>
<li>Granny Smith</li>
<li>Evil Apple of Knowledge</li>
<li>Apple, Inc</li>
</ul>
</figure>
</pre>

You can also label a group of lists using a definition list:

<pre>
<dl>
<dt>Dry:</dt>
<dd>
<ul>
<li>1c flour</li>
<li>1/4c sugar</li>
<li>1tsp baking soda</li>
</ul>
</dd>
<dt>Wet:</dt>
<dd>
<ul>
<li>1 egg </li>
<li>1/2c milk</li>
<li>1tsp vanilla extract</li>
</ul>
</dd>
</dl>
</pre>

These techniques are preferred over adding an <lh> element as proposed in the old HTML3 draft, mostly because of thorny issues with parsing near <li> elements.

=== HTML5 should support a way for anyone to invent new elements! ===

There are actually quite a number of ways for people to invent their own extensions to HTML:

* Authors can use the ''class'' attribute to extend elements, effectively creating their own elements, while using the most applicable existing "real" HTML element, so that browsers and other tools that don't know of the extension can still support it somewhat well. This is the tack used by Microformats, for example.
* Authors can include data for scripts to process using the ''data-*=""'' attributes. These are guaranteed to never be touched by browsers, and allow scripts to include data on HTML elements that scripts can then look for and process.
* Authors can use the ''<meta name="" content="">'' mechanism to include page-wide metadata. Names should be registered on the wiki's [[MetaExtensions]] page.
* Authors can use the ''rel=""'' mechanism to annotate links with specific meanings. This is also used by Microformats. Names should be registered on the wiki's [[RelExtensions]] page.
* Authors can embed raw data using the ''<script type="">'' mechanism with a custom type, for further handling by a script.
* Authors can create plugins and invoke them using the ''<embed>'' element. This is how Flash works.
* Authors can extend APIs using the JS prototyping mechanism. This is widely used by script libraries, for instance.
* Authors can use the microdata feature (the item="" and itemprop="" attributes) to embed nested name-value pairs of data to be shared with other applications and sites.
* Authors can propose new elements and attributes to the working group and, if the wider community agrees that they are worth the effort, they are added to the language. (If an addition is urgent, please let us know when proposing it, and we will try to address it quickly.)

There is currently no mechanism for including non-visible proprietary metadata intended for use by user agents in HTML documents (i.e. for introducing new elements and attributes) without discussing the extension with user agent vendors and the wider Web community. This is intentional; we don't want user agents inventing their own proprietary elements and attributes like in the "bad old days" without working with interested parties to make sure their feature is well designed.

We request that people not invent new elements and attributes to add to HTML without first contacting the working group and getting a proposal discussed with interested parties.

=== HTML5 should group <dt>s and <dd>s together in <di>s! ===

This is a styling problem and should be fixed in CSS. There's no reason to add a grouping element to HTML, as the semantics are already unambiguous.

=== Why are some presentational elements like , and still included? ===

The inclusion of these elements is a largely pragmatic decision based upon their widespread usage, and their usefulness for use cases which are not covered my more specific elements.

While there are a number of common use cases for italics which are covered by more specific elements, such as emphasis (em), citations (cite), definitions (dfn) and variables (var), there are many other use cases which are not covered well by these elements. For example, a taxonomic designation, a technical term, an idiomatic phrase from another language, a thought, or a ship name.

Similarly, although a number of common use cases for bold text are also covered by more specific elements such as strong emphasis (strong), headings (h1-h6) or table headers (th); there are others which are not, such as key words in a document abstract or product names in a review.

Some people argue that in such cases, the span element should be used with an appropriate class name and associated stylesheet. However, the b and i elements provide for a reasonable fallback styling in environments that don't support stylesheets or which do not render visually, such as screen readers, and they also provide some indication that the text is somehow distinct from its surrounding content.

In essence, they convey distinct, though non-specific, semantics, which are to be determined by the reader in the context of their use. In other words, although they don’t convey specific semantics by themselves, they indicate that that the content is somehow distinct from its surroundings and leaves the interpretation of the semantics up to the reader.

This is further explained in the article <cite>[http://lachy.id.au/log/2007/05/b-and-i The and Elements]</cite>

Similarly, the small element is defined for content that is commonly typographically rendered in small print, and which often referred to as fine print. This could include copyright statements, disclaimers and other legal text commonly found at the end of a document.

==== But they are PRESENTATIONAL! ====

While , and historically have been presentational, they are defined in a media-independent manner in HTML5. For example, corresponds to the really quickly spoken part at the end of radio advertisements. The problem with elements like isn't that they are ''presentational'' per se, it's that they are media-dependent (they apply to visual browsers but not to speech browsers).

== WHATWG and the W3C HTML WG ==

=== Are there plans to merge the groups? ===

Not especially. There are people who for a number of reasons are unable to join the W3C group, and there are others who are unable to join the WHATWG group. The editor is in both groups and takes all input into account -- and there are far more places where input on HTML5 is sent than just these two mailing lists (e.g. blogs, www-html@w3.org, forums, direct mail, meetings, etc).

=== Which group has authority in the event of a dispute? ===

The editor takes feedback from everyone into account and does not look at the source of those arguments for technical arguments.

=== What is the history of HTML? ===

Here are some documents that detail the history of HTML:
* [http://esw.w3.org/topic/HTML/history HTML's timeline on the ESW wiki]
* [http://www.whatwg.org/specs/web-apps/current-work/multipage/introduction.html#history0 The history section in HTML5 itself]

== Mailing List ==

=== Should I top-post or reply inline? ===

Please reply inline or make the reply self-contained.

Basically, please remove anything after the last line you have written, so that people don't have to scroll down to find out what else you wrote, and make sure that your e-mail makes sense on its own, as it will probably be read out of context years later.

That is, you should reply like this:

<pre>
Ian wrote:
> What do you want?

I want cats!

> When do you want it?

Now!
</pre>

You should definitely not reply like this (because this requires people to read your e-mail backwards):

<pre class="error" >
No

Ian wrote:
> Is this a good example of how to post e-mails?
</pre>

You should also not reply like this (because this leaves people to wonder if there is any text lower down that you have written):

<pre class="error" >
This is a bad way to write e-mail.

Ian wrote:
> Is this a good way to write e-mail?
> Lorem ipsum foo bar baz.
> Unrelated other bits that aren't replied to.
> Yet more text
</pre>

You should also not reply like this (with no context at all), because the reader will not know what you are referring to:

<pre class="error" >
No, I think that's a bad idea. It wouldn't be good for the readers, for instance.
</pre>

Quote enough original text or provide an introduction yourself.

If you use Outlook or Outlook Express, you can use either [http://home.in.tum.de/~jain/software/outlook-quotefix/ Outlook-QuoteFix] or [http://home.in.tum.de/~jain/software/oe-quotefix/ OE-QuoteFix]. These plugins fix several of Outlook's problems with sending properly formatted emails.

User:Sbp

2008-02-01T16:17:02Z

Sbp: Adding rather scant details.

Name: Sean B. Palmer

RelExtensions

2008-02-01T16:11:38Z

Sbp: Proposal: profile.

This page lists the allowed extension values for the rel="" attribute in HTML5. You may add your own values to this list, which makes them legal HTML5 rel values. We ask that you try to avoid redundancy; if someone has already defined a value that does roughly what you want, please reuse it.

{|
! rowspan=2 | Keyword
! colspan=2 | Effect on...
! rowspan=2 | Brief description
! rowspan=2 | Link to more details
! rowspan=2 | Synonyms
! rowspan=2 | Status
|-
! link
! a and area
|-
| script
| not allowed
| not allowed
| Was proposed to replace <script>. Use <script> instead.
| none
|
| Rejected
|-
| glossary
| hyperlink
| hyperlink
| Target document provides definitions for words in current document.
| [http://www.w3.org/TR/html4/types.html#h-6.12 HTML4]
|
| Proposal
|-
| chapter
| hyperlink
| hyperlink
| Target document is a subdocument of the current document.
| [http://www.w3.org/TR/html4/types.html#h-6.12 HTML4]
| section, subsection, appendix
| Proposal
|-
| edit
| hyperlink
| hyperlink
| Target document is an editable version of the current document.
| [http://bitworking.org/projects/atom/draft-ietf-atompub-protocol-11.html#new-link-relation Atom Protocol]
|
| Proposal
|-
| openid.server
| external resource
| not allowed
| OpenID authentication delegation
| [http://openid.net/specs/openid-authentication-1_1.html#delegating_authentication OpenID specificaion]
|
| Proposal
|-
| openid.delegate
| external resource
| not allowed
| OpenID authentication delegation
| [http://openid.net/specs/openid-authentication-1_1.html#delegating_authentication OpenID specificaion]
|
| Proposal
|-
| widget
| hyperlink
| hyperlink
| Points to a widget.
| [http://dev.w3.org/2006/waf/widgets/Overview.html#autodiscovery Widgets 1.0 Editor's draft]
|
| Proposal
|-
| service
| external resource
| not allowed
| Points to a resource describing a service API
| [[ServiceRelExtension]]
|
| Proposal
|-
| acquaintance
| hyperlink
| hyperlink
| the person represented by the current document considers the person represented by the referenced document to be an acquaintance
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| child
| hyperlink
| hyperlink
| the referenced person is a child of the person represented by the current document
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| colleague
| hyperlink
| hyperlink
| the referenced person is a colleague of the person represented by the current document
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| contact
| hyperlink
| hyperlink
| the person represented by the current document considers the person represented by the referenced document to be a contact
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| co-resident
| hyperlink
| hyperlink
| the referenced person lives in the same residence as the person represented by the current document
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| co-worker
| hyperlink
| hyperlink
| the referenced person is a co-worker of the person represented by the current document
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| crush
| hyperlink
| hyperlink
| this person considers the referenced person to be a crush (i.e. has a crush on the referenced person)
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| date
| hyperlink
| hyperlink
| this person considers the referenced person to be a date (i.e. is dating the referenced person)
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| friend
| hyperlink
| hyperlink
| the person represented by the current document considers the person represented by the referenced document to be a friend
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| kin
| hyperlink
| hyperlink
| the referenced person is part of the extended family of the person represented by the current document
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| me
| hyperlink
| hyperlink
| the referenced document represents the same person as does the current document
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| met
| hyperlink
| hyperlink
| this person has met the referenced person
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| muse
| hyperlink
| hyperlink
| the referenced person inspires the person represented by the current document
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| neighbor
| hyperlink
| hyperlink
| the referenced person lives nearby the person represented by the current document
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| parent
| hyperlink
| hyperlink
| the referenced person is a parent of the person represented by the current document
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| sibling
| hyperlink
| hyperlink
| the referenced person is a sibling of the person represented by the current document
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| spouse
| hyperlink
| hyperlink
| the referenced person is a spouse of the person represented by the current document
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| sweetheart
| hyperlink
| hyperlink
| this person considers the referenced person to be their sweetheart
| [http://gmpg.org/xfn/11 XFN]
|
| Proposal
|-
| profile
| hyperlink
| not allowed
| this referenced link is a metadata profile for the current document
| [http://www.w3.org/TR/html401/struct/global.html#profiles HTML Meta data profiles]
|
| Proposal
|}

The "Effect on... link" column must either say "not allowed" if the rel value is not allowed on <link> elements, "hyperlink" if the rel value creates a hyperlink, or "external resource" if the rel value creates a link to an external resource.

The "Effect on... a and area" column must either say "not allowed" or "hyperlink".

For the "Status" section to be changed to "Accepted", the proposed keyword must have been through the [http://microformats.org/wiki/process Microformats process], and been approved by the Microformats community.

For more details, see [http://whatwg.org/specs/web-apps/current-work/#linkTypes the HTML5 specification]. See also [http://microformats.org/wiki/existing-rel-values the Microformats wiki page on this matter].