WHATWG Wiki - User contributions [en]

RelExtensions

2008-10-30T07:31:56Z

RyanKing: adding wlwmanifest to the list

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
|-
| help
| hyperlink
| hyperlink
| Refers to a document offering help (more information, links to other sources information, etc.)
| [http://www.w3.org/TR/html4/types.html#h-6.12 HTML4]
|
| Redundant - defined in HTML5
|-
| prev
| hyperlink
| hyperlink
| Refers to the previous document in an ordered series of documents.
| [http://www.w3.org/TR/html4/types.html#h-6.12 HTML4]
|
| Redundant - defined in HTML5
|-
| next
| hyperlink
| hyperlink
| Refers to the next document in a linear sequence of documents.
| [http://www.w3.org/TR/html4/types.html#h-6.12 HTML4]
|
| Redundant - defined in HTML5
|-
| 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 1.1 authentication delegation
| [http://openid.net/specs/openid-authentication-1_1.html#delegating_authentication OpenID specificaion]
|
| Proposal
|-
| openid.delegate
| external resource
| not allowed
| OpenID 1.1 authentication delegation
| [http://openid.net/specs/openid-authentication-1_1.html#delegating_authentication OpenID specificaion]
|
| Proposal
|-
| openid2.provider
| external resource
| not allowed
| OpenID 2.0 authentication endpoint
| [http://openid.net/specs/openid-authentication-2_0.html#html_disco OpenID Auth 2.0 section 7.3.3]
|
| Proposal
|-
| openid2.local_id
| external resource
| not allowed
| OpenID 2.0 authentication delegation
| [http://openid.net/specs/openid-authentication-2_0.html#html_disco OpenID Auth 2.0 section 7.3.3]
|
| 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
|-
| timesheet
| external resource
| not allowed
| SMIL Timesheet
| [http://www.w3.org/TR/timesheets/#smilTimesheetsNS-Elements-Timesheet SMIL Timesheets 1.0]
|
| Proposal
|-
| license
| hyperlink
| hyperlink
| The linked document is a license for the current document
| [http://microformats.org/wiki/rel-license rel-license]
|
| Proposal
|-
| tag
| hyperlink
| hyperlink
| The linked document is an author-designated "tag" (or keyword/subject) for the current page.
| [http://microformats.org/wiki/rel-tag rel-tag]
|
| Proposal
|-
| author
| hyperlink
| hyperlink
| The linked document is the page/email an agent (people or firm or...) responsible for the content.
|
|
| Proposal
|-
| contributor
| hyperlink
| hyperlink
| The linked document is the page/email an agent (people or firm or...) involved in the production of the content, but not his main author(s).
|
|
| Proposal
|-
| webmaster
| hyperlink
| hyperlink
| The linked document is the page/email an agent (people or firm or...) aviable for requests about the content of the page.
|
| maintainer
| Proposal
|-
| translator
| hyperlink
| hyperlink
| The linked document is the page/email an agent (people or firm or...) responsible for the translation of the page.
|
|
| Proposal
|-
| technicalAuthor
| hyperlink
| hyperlink
| The linked document is the page/email an agent (people or firm or...) responsible for the technical construction of the page (i.e. the HTML/CSS/PHP code), not for the content.
|
|
| Proposal
|-
| EditURI
| hyperlink
| not allowed
| a link to an RSD file describing how to edit the given page.
| [http://cyber.law.harvard.edu/blogs/gems/tech/rsd.htm rsd]
|
| Proposal
|-
| wlwmanifest
| hyperlink
| not allowed
| A link to a manifest for Windows Live Writer.
| [http://msdn.microsoft.com/en-us/library/bb463263.aspx msdn}
|
| 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 either have been through the [http://microformats.org/wiki/process Microformats process], and been approved by the Microformats community; or must be defined by a W3C specification in the Candidate Recommendation or Recommendation state.

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].

RelExtensions

2008-10-30T07:29:41Z

RyanKing: adding EditURI to list

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
|-
| help
| hyperlink
| hyperlink
| Refers to a document offering help (more information, links to other sources information, etc.)
| [http://www.w3.org/TR/html4/types.html#h-6.12 HTML4]
|
| Redundant - defined in HTML5
|-
| prev
| hyperlink
| hyperlink
| Refers to the previous document in an ordered series of documents.
| [http://www.w3.org/TR/html4/types.html#h-6.12 HTML4]
|
| Redundant - defined in HTML5
|-
| next
| hyperlink
| hyperlink
| Refers to the next document in a linear sequence of documents.
| [http://www.w3.org/TR/html4/types.html#h-6.12 HTML4]
|
| Redundant - defined in HTML5
|-
| 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 1.1 authentication delegation
| [http://openid.net/specs/openid-authentication-1_1.html#delegating_authentication OpenID specificaion]
|
| Proposal
|-
| openid.delegate
| external resource
| not allowed
| OpenID 1.1 authentication delegation
| [http://openid.net/specs/openid-authentication-1_1.html#delegating_authentication OpenID specificaion]
|
| Proposal
|-
| openid2.provider
| external resource
| not allowed
| OpenID 2.0 authentication endpoint
| [http://openid.net/specs/openid-authentication-2_0.html#html_disco OpenID Auth 2.0 section 7.3.3]
|
| Proposal
|-
| openid2.local_id
| external resource
| not allowed
| OpenID 2.0 authentication delegation
| [http://openid.net/specs/openid-authentication-2_0.html#html_disco OpenID Auth 2.0 section 7.3.3]
|
| 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
|-
| timesheet
| external resource
| not allowed
| SMIL Timesheet
| [http://www.w3.org/TR/timesheets/#smilTimesheetsNS-Elements-Timesheet SMIL Timesheets 1.0]
|
| Proposal
|-
| license
| hyperlink
| hyperlink
| The linked document is a license for the current document
| [http://microformats.org/wiki/rel-license rel-license]
|
| Proposal
|-
| tag
| hyperlink
| hyperlink
| The linked document is an author-designated "tag" (or keyword/subject) for the current page.
| [http://microformats.org/wiki/rel-tag rel-tag]
|
| Proposal
|-
| author
| hyperlink
| hyperlink
| The linked document is the page/email an agent (people or firm or...) responsible for the content.
|
|
| Proposal
|-
| contributor
| hyperlink
| hyperlink
| The linked document is the page/email an agent (people or firm or...) involved in the production of the content, but not his main author(s).
|
|
| Proposal
|-
| webmaster
| hyperlink
| hyperlink
| The linked document is the page/email an agent (people or firm or...) aviable for requests about the content of the page.
|
| maintainer
| Proposal
|-
| translator
| hyperlink
| hyperlink
| The linked document is the page/email an agent (people or firm or...) responsible for the translation of the page.
|
|
| Proposal
|-
| technicalAuthor
| hyperlink
| hyperlink
| The linked document is the page/email an agent (people or firm or...) responsible for the technical construction of the page (i.e. the HTML/CSS/PHP code), not for the content.
|
|
| Proposal
|-
| EditURI
| hyperlink
| not allowed
| a link to an RSD file describing how to edit the given page.
| [http://cyber.law.harvard.edu/blogs/gems/tech/rsd.htm rsd]
|
| proposed
|}

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 either have been through the [http://microformats.org/wiki/process Microformats process], and been approved by the Microformats community; or must be defined by a W3C specification in the Candidate Recommendation or Recommendation state.

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].

Parser tests

2007-10-12T18:45:07Z

RyanKing: /* Tree Construction Tests */ added tree construction test format issues

=Parser Tests=

This page documents the unit-test format(s) being used for implementations of the HTML5 parsing spec. The aim is to produce implementation-independent, self-describing tests that can be shared between any groups working on these technologies.

==Tokenizer Tests==
The test format is [http://www.json.org/ JSON]. This has the advantage that the syntax allows backward-compatible extensions to the tests and the disadvantage that it is relatively verbose.

===Basic Structure===

{"tests": [

{"description":"Test description",
"input":"input_string",
"output":[expected_output_tokens]},
"contentModelFlags":[content_model_flags],
"lastStartTag":last_start_tag,
"ignoreErrorOrder":ignore_error_order
]}

<tt>description</tt>, <tt>input</tt> and <tt>output</tt> are always present. The other values are optional.

<tt>input_string</tt> is a string literal containing the input string to pass to the tokenizer.

<tt>expected_output_tokens</tt> is a list of tokens, ordered with the first produced by the tokenizer the first (leftmost) in the list. The list must mach the '''complete''' list of tokens that the tokenizer should produce. Valid tokens are:

["DOCTYPE", name, public_id, system_id, correctness]
["StartTag", name, {attributes}])
["EndTag", name]
["Comment", data]
["Character", data]
"ParseError"

<tt>public_id</tt> and <tt>system_id</tt> are either strings or <tt>null</tt>. <tt>correctness</tt> is either <tt>true</tt> (correct) or <tt>false</tt> (incorrect).

<tt>content_model_flags</tt> is a list of strings from the set:
PCDATA
RCDATA
CDATA
PLAINTEXT
The test case applies when the tokenizer begins with its content model flag set to any of those values. If <tt>content_model_flags</tt> is omitted, it defaults to <tt>["PCDATA"]</tt>.

<tt>last_start_tag</tt> is a lowercase string that should be used as "the tag name of the last start tag token emitted" in the tokenizer algorithm. If it is omitted, it is treated as if "no start tag token has ever been emitted by this instance of the tokeniser".

<tt>ignore_error_order</tt> is a boolean value indicating that the order of <tt>ParseError</tt> tokens relative to other tokens in the output stream is unimportant, and implementations should ignore such differences between their output and <tt>expected_output_tokens</tt>. (This is used for errors emitted by the input stream preprocessing stage, since it is useful to test that code but it is undefined when the errors occur). If it is omitted, it defaults to <tt>false</tt>.

Multiple tests per file are allowed simply by adding more objects to the "tests" list.

All adjacent character tokens are coalesced into a single <tt>["Character", data]</tt> token.

=== Open Issues ===
* Is the format too verbose?
* Do we want to allow the test to pass if only a subset of the actual tokens emitted matches the expected_output_tokens list?

==Tree Construction Tests==

Each file containing tree construction tests consists of any number of tests separated by two newlines (LF) and a single newline before the end of the file. For instance:

<pre>[TEST]LF
LF
[TEST]LF
LF
[TEST]LF</pre>

Where [TEST] is the following format:

Each test must begin with a string "#data" followed by a newline (LF). All subsequent lines until a line that says "#errors" are the test data and must be passed to the system being tested unchanged, except with the final newline (on the last line) removed. Then there must be a line that says "#errors". It must be followed by one line per parse error that a conformant checker would return. It doesn't matter what those lines are, the only thing that matters is that there be the right number of parse errors. Then there must be a line that says "#document", which must be followed by a dump of the tree of the parsed DOM. Each node must be represented by a single line. Each line must start with "| ", followed by two spaces per parent node that the node has before the root document node. Element nodes must be represented by a "<" then the tag name then ">", and all the attributes must be given, sorted lexicographically by UTF-16 code unit, on subsequent nodes, as if they were children of the element node. Attribute nodes must have the attribute name, then an "=" sign, then the attribute value in double quotes ("). Text nodes must be the string, in double quotes. Newlines aren't escaped. Comments must be "<" then "!-- " then the data then " -->". DOCTYPEs must be "<!DOCTYPE " then the name then ">".

For example:
<pre>
#data
<p>One<p>Two
#errors
3: Missing document type declaration
#document
| <html>
| <head>
| <body>
| <p>
| "One"
| <p>
| "Two"
</pre>

Tests can be found here: http://html5lib.googlecode.com/svn/trunk/testdata/tree-construction/

=== Open Issues ===
* document-fragment isn't specified
* should relax the order constraint?

HTML vs. XHTML

2006-12-13T23:34:48Z

RyanKing: /* Differences Between HTML 4.01 and HTML 5 */ added a list of dropped attributes

== Differences Between HTML and XHTML ==

'''Please note that the information in here is based upon the current spec for (X)HTML5. Some of the issues technically do not apply to previous versions of HTML.'''

Although HTML and XHTML appear to have similarities in their syntax, they are significantly different in many ways.

'''Note''': As the current WHATWG document is a draft, this section will need to track to a moving target.
Differences marked @@@ are differences that could theoretically be changed without affecting backwards compatibility.

=== MIME Types ===

* XHTML must be served with an XML MIME type, such as <code>application/xml</code> or <code>application/xhtml+xml</code>.
* HTML must be served as <code>text/html</code>.

It is the MIME type that determines what type of document you are using. If you use attempt to send XHTML as <code>text/html</code>, you are actually just using HTML, possibly with syntax errors.

Technically, according to the spec, XHTML 1.0 is allowed to be served as <code>text/html</code>. But, due to the above reason, such a document is considered to be an HTML document, not an XHTML document.

=== Parsing ===

XHTML uses XML parsing requirements. HTML uses its own which are defined much more closely to the way browsers actually handle HTML today.

* In XHTML, well-formedness errors are fatal. In HTML, error handling rules are much more graceful. Well-formedness errors, which are also syntax errors in HTML, include the following:
** Unencoded ampersands (<code>&</code>) and less than signs (<code><</code>) (This does not apply to <code>CDATA</code>).
** Comments containing extra pairs of hyphens or ending with a hyphen. e.g.
*** <code></code> or
*** <code></code>.
** Mismatched end tags (does not apply to elements with optional tags)
** Unclosed tags.
** Unexpected characters occuring in or before attribute names.
** Unexpected occurrence of EOF.
** Unexpected characters before the DOCTYPE name.
** Missing DOCTYPE name.
** A <code>PUBLIC</code> identifer in a <code>DOCTYPE</code> without a <code>SYSTEM</code> identifier (Note: including either of these is a syntax error in HTML5; but, in XML only the <code>SYSTEM</code> identifier is allowed to occur on its own).
** End tags with attributes.
** Unexpected end tags (in HTML, an unexpected <code></br></code> or <code></p></code> can cause the start tag to be implied before it).
* The internal subset is permitted in XML, but meaningless (and forbidden) in HTML.
** In some cases, an internal subset in HTML would end up being partly rendered inline.
* The sequence of characters "<code>]]></code>" when it does not mark the end of a <code>CDATA</code> section is a well-formedness error in XHTML, but valid in HTML.
* In XHTML: <code><![CDATA[...]]></code> is a <code>CDATA</code> section. In HTML, it's a bogus comment.
* In XHTML, <code><?foo ...?></code> is a processing instruction. In HTML, it's a bogus comment.
* In HTML, the trailing slash used for the empty element syntax is a parse error for non-void elements (see below), but is ignored in all cases.
* In HTML, the <code>script</code> and <code>style</code> elements are parsed as <code>CDATA</code>. (Note: the definition of <code>CDATA</code> differs from that in XML). In XML, they're parsed as normal elements (which means that comments are treated as <em>real</em> comments, and things that look like start tags actually are start tags).
* In HTML, the <code>title</code> and <code>textarea</code> elements are parsed as <code>RCDATA</code>. (Note: The definition of <code>RCDATA</code> differs from that in SGML and there is no <code>RCDATA</code> in XML).
* In HTML, if scripting is enabled, the <code>noscript</code> element is parsed as <code>CDATA</code>. If scripting is disabled, it's parsed as <code>PCDATA</code>. In XHTML, the element has no effect, and can't really be used to stop content from being present when script is disabled.
* In HTML, the <code>iframe</code>, <code>noembed</code> and <code>noframes</code> elements are parsed as <code>CDATA</code>. In XHTML, they are parsed as normal elements, and therefore do not stop content from being used.
* White space characters in attribute values are [http://www.w3.org/TR/REC-xml/#AVNormalize normalized] to spaces in XHTML.
* Elements with optional tags are implied in certain conditions.
* In HTML, <code>base</code>, <code>link</code>, <code>meta</code>, <code>style</code> and <code>title</code> elements with tags occurring in the body are moved inserted into the head. In XHTML, they stay where they were specified.
* In HTML, tags for certain elements, which appear out of context, are ignored. This includes <code>caption</code>, <code>col</code>, <code>colgroup</code>, <code>frame</code>, <code>frameset</code>, <code>head</code>, <code>option</code>, <code>optgroup</code>, <code>tbody</code>, <code>td</code>, <code>tfoot</code>, <code>th</code>, <code>thead</code>, <code>tr</code>.
* The <code>plaintext</code> element has a special parsing requirement in HTML. (it is, however, forbidden).
* <em>Many other special handling of edge cases and error conditions, not all of which are listed here, occur in HTML.</em>

=== Syntax ===

* In HTML, [http://blog.whatwg.org/faq/#doctype the <code>doctype</code> is required]. In XHTML, it is optional.
* In XHTML, tag names and attribute names are case sensitive. In HTML, they are case insensitive.
* In XHTML, non-empty elements require both a start and an end tag. In HTML, certain elements allow the omission of either or both:
** <code>html</code> (both)
** <code>head</code> (both)
** <code>body</code> (both)
** <code>li</code> (end tag)
** <code>dt</code> (end tag)
** <code>dd</code> (end tag)
** <code>p</code> (end tag)
** <code>colgroup</code> (both)
** <code>thead</code> (end tag)
** <code>tbody</code> (both)
** <code>tfoot</code> (end tag)
** <code>tr</code> (end tag)
** <code>td</code> (end tag)
** <code>th</code> (end tag)
* In XHTML, empty elements may use either the empty element syntax (<code><br/></code>) or have an end tag immediately follow the start tag (<code><br></br></code>). In HTML, the empty element syntax (trailing slash) is allowed on void elements, but forbidden on other elements. However, it serves no purpose whatsoever and can be omitted. End tags for void elements are forbidden.
** <code>base</code>,<code> link</code>, <code>meta</code>, <code>hr</code>, <code>br</code>, <code>img</code>, <code>embed</code>, <code>param</code>, <code>area</code>, <code>col</code> and <code>input</code>
** Note: the following are treated as void elements for the purpose in the parsing requirements, but, as they are obsolete and non-standard, the trailing slash is not permitted: <code>basefont</code>, <code>b</code><code>gsound</code>, <code>spacer</code>, <code>wbr</code>. (although, since these elements are not permitted anyway, it doesn't make much difference).
* HTML allows attribute minimisation (i.e. omitting the value), XHTML does not.
* HTML allows the use of unquoted attribute values, XHTML does not.
* XHTML allows the use of <code>CDATA</code> sections, HTML does not.
* XHTML allows the use of processing instructions, HTML does not.
* In HTML, all entity references are predefined and do not require a DTD. But because there is no DTD for XHTML5, entity references cannot be used in XHTML. (excluding the 5 predefined entities: <code>&amp;</code>, <code>&lt;</code>, <code>&gt;</code>, <code>&quot;</code> and <code>&apos;)</code>
** You may provide your own DTD for use with your own validating parser, but be aware that browsers do not use validating parsers and will not read the DTD.
* The valid set of unicode characters in XML 1.0 is limited beyond that in HTML.
* Namespace prefixes are permitted in XHTML. They are forbidden in HTML.

=== Markup ===

* The [http://blog.whatwg.org/faq/#namespace-decl namespace declaration] (<code>xmlns</code> attribute) is required in XHTML. The xmlns attribute is also allowed to appear on the <code>html</code> element in HTML on the condition that is has the value <code><nowiki>"http://www.w3.org/1999/xhtml"</nowiki></code>.
** <code><nowiki><html xmlns="http://www.w3.org/1999/xhtml"></nowiki></code>
** In HTML, the xmlns attribute has absolutely no effect. It is basically a talisman. It is allowed merely to make migration to and from XHTML mildly easier. When parsed by an HTML parser, the attribute ends up in the null namespace
** In XML (with an [http://www.w3.org/TR/xml-names/ XML Namespaces]-aware parser), an xmlns attribute is part of the namespace declaration mechanism, and an element cannot actually have an xmlns attribute in the null namespace. In DOM implementations, the attribute ends up in the "<code><nowiki>http://www.w3.org/2000/xmlns/</nowiki></code>" namespace.
* XHTML allows non XHTML elements and attributes (in different namespaces) to be used, HTML does not.
* XHTML uses the <code>xml:lang</code> attribute, HTML uses <code>lang</code> instead,
* XML ID introduces <code>xml:id</code>, which could be used in XHTML. In HTML it has no effect.
* In HTML, the <code>noscript</code> element may be used. In XHTML, it is forbidden.
* HTML uses the <code>base</code> element, XHTML uses <code>xml:base</code> instead.
* In XHTML, <code>p</code> elements may contain structured inline level elements including <code>blockquote</code>, <code>dl</code>, <code>menu</code>, <code>ol</code>, <code>ul</code>, <code>pre</code> and <code>table</code>. In the HTML serialisation, due to backwards compatibility constraints, this is not possible (though it may be done through DOM manipulation).
* In XHTML, <code>table</code> elements may contain child <code>tr</code> elements. In the HTML serialisation, due to backwards compatibility constraints, this is not possible (though it may be done through DOM manipulation).

=== Character Encoding ===

* In XHTML, the XML declaration may be used to [http://blog.whatwg.org/faq/#charset specify the character encoding]. In HTML, the xml declaration is forbidden
* In HTML, the <code>meta</code> element may be used insted. The <code>http-equiv</code> attribute on the <code>meta</code> element is forbidden in XHTML and is ignored if included.
* The default character encoding for XHTML is, according to XML rules, <code>UTF-8</code> or <code>UTF-16</code>. If the encoding is unspecified in HTML, it should be determined through implementation specific heuristics or fallback to a default value (Note: this section of the spec is not yet finished).

=== Scripts ===

* <code>document.write()</code> and <code>document.writeln()</code> cannot be used in XHTML, they can in HTML.
* In XHTML, the use of the <code>innerHTML</code> property requires that the string be a well-formed fragment of XML.
* DOM APIs are case sensitive in XHTML and some are case insensitive in HTML. (This does not apply to elements which are not in the HTML namespace)
** Element.tagName, Node.nodeName, and Node.localName return the value in uppercase.
** Document.createElement() is case insensitive (the canonical form is lowercase).
** Element.setAttributeNode() will change the attribute name to lowercase.
** Element.setAttribute() is case insensitive (the canonical form is lowercase).
** Document.getElementsByTagName() and Element.getElementsByTagName() are case insensitive.
** Document.renameNode(). If the new namespace is the HTML namespace, then the new qualified name must be lowercased before the rename takes place.
* In HTML, Document.createElement() will create an element in the HTML namespace. In XML (including XHTML), the namespace is defined by both DOM2 and DOM3 to be null.
** In XHTML, browsers lack interoperability in this area. In Firefox, the namespace is dependent upon the MIME type. In Opera, it's dependent upon the root element and in Safari, it's always null.

=== Stylesheets ===

* Selectors, as used in CSS, match case sensitively in XHTML, but case insensitively in HTML.
* CSS requires special handling of the body element in HTML for painting backgrounds on the canvas, which do not apply to XHTML.

== Differences Between HTML 4.01 and HTML 5 ==

=== MIME Type ===

Both HTML 4.01 and HTML 5 use <code>text/html</code>.

<code>Content-Type: text/html; charset=UTF-8</code>

=== Parsing HTML ===

* HTML 2.0 to HTML 4.01 were formally based on SGML, but browsers did not implement SGML parsers. [http://www.w3.org/TR/html4/conform.html#h-4.2 4.2 SGML] and [http://www.w3.org/TR/html4/appendix/notes.html#h-B.3 B.3 SGML implementation notes], HTML 4.01. This is a non-normative section of HTML 4.01 specification. And it already makes the difference between HTML user agents and SGML user agents.
* HTML 5 is defines its own parsing requirements based on the way browsers actually handle HTML.

=== Syntax ===

* TODO

=== Markup ===

* [http://www.w3.org/TR/html4/index/elements.html List of HTML 4.01 elements]
* [http://www.w3.org/TR/html4/index/attributes.html List of HTML 4.01 attributes]
* No list (elements and attributes) yet for Web Apps 1.0

==== Dropped Attributes ====

Some HTML 4 attributes are being dropped in HTML5. Here's a current list (subject to change, see the spec):

* head@profile
* a@rev
* link@rev
* td@headers
* td@axis
* th@headers
* th@axis
* table@summary

=== Character Encoding ===

==== HTML 4 Algorithm ====

Source [http://www.w3.org/TR/html4/charset.html#h-5.2.2 5.2.2 Specifying the character encoding], HTML 4.01 Specification.

# An HTTP "charset" parameter in a "Content-Type" field.
# A META declaration with "http-equiv" set to "Content-Type" and a value set for "charset".
# The charset attribute set on an element that designates an external resource.

==== HTML 5 Algorithm ====

This is currently undefined in the spec. See [[Character Encoding Detection]] for documentation.

== Differences Between DOM Level 2.0, 3.0 and the HTML 5 DOM APIs ==

'''This section might belong on a separate page.'''

* TODO (need to talk about the changes to the DOM API that HTML5 is making, compared with DOM2 and DOM3)