Difference between revisions of "Document type declaration"
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The DOCTYPE is retained in HTML5 as a "mostly useless, but required" header only to trigger "standards mode" in common browsers. | The DOCTYPE is retained in HTML5 as a "mostly useless, but required" header only to trigger "standards mode" in common browsers. | ||
| + | |||
| + | == Syntax == | ||
| + | |||
| + | The general syntax for a document type declaration is: | ||
| + | |||
| + | <pre> | ||
| + | <!DOCTYPE root-element PUBLIC "FPI" ["URI"] [ | ||
| + | <!-- internal subset declarations --> | ||
| + | ]> | ||
| + | </pre> | ||
| + | |||
| + | or | ||
| + | |||
| + | <pre> | ||
| + | <!DOCTYPE root-element SYSTEM "URI" [ | ||
| + | <!-- internal subset declarations --> | ||
| + | ]> | ||
| + | </pre> | ||
== See also == | == See also == | ||
| Line 24: | Line 42: | ||
* [[SGML]] | * [[SGML]] | ||
* [[XHTML]] | * [[XHTML]] | ||
| − | * [[XML]] | + | * [[XML]] |
== External Links == | == External Links == | ||
Latest revision as of 04:47, 15 May 2016
A document type declaration, or DOCTYPE, is an instruction that associates a particular SGML or XML document (for example, a web page) with a document type definition (DTD) (for example, the formal definition of a particular version of HTML).
Description
In the serialized form of the document, it manifests as a short string of markup that conforms to a particular syntax.
The HTML layout engines in modern web browsers perform DOCTYPE "sniffing" or "switching", wherein the DOCTYPE in a document served as text/html determines a layout mode, such as "quirks mode" or "standards mode".
Since web browsers are implemented with special-purpose HTML parsers, rather than general-purpose DTD-based parsers, they don't use DTDs and will never access them even if a URL is provided.
HTML5
The text/html serialization of HTML5, which is not SGML-based, uses the DOCTYPE only for mode selection.
The DOCTYPE is retained in HTML5 as a "mostly useless, but required" header only to trigger "standards mode" in common browsers.
Syntax
The general syntax for a document type declaration is:
<!DOCTYPE root-element PUBLIC "FPI" ["URI"] [ <!-- internal subset declarations --> ]>
or
<!DOCTYPE root-element SYSTEM "URI" [ <!-- internal subset declarations --> ]>
See also
External Links
- Document type declaration @ Wikipedia
