Choosing a DOCTYPE

客官°小女子只卖身不卖艺 2022-07-17 00:39 178阅读 0赞

原文链接：[http://www.htmlhelp.com/tools/validator/doctype.html][http_www.htmlhelp.com_tools_validator_doctype.html]

According to HTML standards, each HTML document requires a *document typedeclaration*. The "DOCTYPE" begins the HTML document and tells a [validator][] which version of HTML to use inchecking the document's syntax.

If standard HTML does not meet your needs but you still wish to gain thebenefits of HTML validation, see the section on [ using a custom DTD][using a custom DTD].

The following DOCTYPEs are commonly used:

**<!DOCTYPE HTMLPUBLIC "-//W3C//DTD HTML 4.01//EN"  
"http://www.w3.org/TR/html4/strict.dtd">**

This declares the document to be  **HTML 4.01 Strict**. HTML 4.01 Strictis a trimmed down version of [ HTML 4.01][HTML 4.01] that emphasizes structure overpresentation. [ Deprecated elements][Deprecated elements] and attributes (includingmost presentational attributes), [frames][], and link targets are not allowed in HTML 4 Strict. Bywriting to HTML 4 Strict, authors can achieve accessible, structurally richdocuments that easily adapt to [ style sheets][style sheets] and different browsing situations.However, HTML 4 Strict documents may look bland on very old browsers that lacksupport for style sheets.

Newer browsers such as Internet Explorer 5 for Mac, Netscape 6, and [Mozilla][] usea standards-compliant rendering for HTML 4 Strict documents. These browsers usea "quirks" mode for most other document types to emulate renderingbugs in older browsers.

**<!DOCTYPE HTMLPUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"  
"http://www.w3.org/TR/html4/loose.dtd">**

This declares the document to be  **HTML 4.01 Transitional**. HTML 4Transitional includes all elements and attributes of [ HTML 4 Strict][HTML 4 Strict] but adds presentational attributes,[deprecated elements][Deprecated elements], and link targets.

Newer browsers such as Internet Explorer 5 for Mac, Netscape 6, and [Mozilla][] usea standards-compliant rendering for HTML 4.01 Transitional documents thatinclude the URI of the DTD in the DOCTYPE. These browsers use a"quirks" mode to emulate rendering bugs in older browsers if the URIis omitted:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01Transitional//EN">

**<!DOCTYPE HTMLPUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN"  
"http://www.w3.org/TR/html4/frameset.dtd">**

This declares the document to be  **HTML 4.01 Frameset**. HTML 4 Framesetis a variant of [ HTML 4 Transitional][HTML 4 Transitional] for documents that use [ frames][frames].

**<!DOCTYPE htmlPUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"  
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">**

This declares the document to be  **XHTML 1.0 Strict**. [ XHTML 1.0][XHTML 1.0]Strict is an XML version of [ HTML 4 Strict][HTML 4 Strict].

**<!DOCTYPE htmlPUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"  
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">**

This declares the document to be  **XHTML 1.0 Transitional**. [ XHTML 1.0][XHTML 1.0]Transitional is an XML version of [ HTML 4 Transitional][HTML 4 Transitional].

**<!DOCTYPE htmlPUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN"  
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">**

This declares the document to be  **XHTML 1.0 Frameset**. [ XHTML 1.0][XHTML 1.0]Frameset is an XML version of [ HTML 4 Frameset][HTML 4 Frameset].

**<!DOCTYPE HTML PUBLIC"-//W3C//DTD HTML 3.2 Final//EN">**

This declares the document to be  **HTML 3.2**. [ HTML3.2][HTML3.2] is well supported by most browsers in use. However, HTML 3.2 haslimited support for [style sheets][] and no support for [HTML4][] features such as [frames][] and internationalization.

**<!DOCTYPE HTML PUBLIC"-//IETF//DTD HTML//EN">**

This declares the document to be  **HTML 2.0**. [ HTML 2.0][HTML 2.0]is widely supported by browsers but lacks support for tables, frames, andinternationalization, as well as many commonly used presentational elements andattributes.

[http_www.htmlhelp.com_tools_validator_doctype.html]: http://www.htmlhelp.com/tools/validator/doctype.html
[validator]: http://www.htmlhelp.com/tools/validator/index.html.en
[using a custom DTD]: http://www.htmlhelp.com/tools/validator/customdtd.html
[HTML 4.01]: http://www.w3.org/TR/html401/
[Deprecated elements]: http://www.htmlhelp.com/reference/html40/deprecated.html
[frames]: http://www.htmlhelp.com/reference/html40/frames/
[style sheets]: http://www.htmlhelp.com/reference/css/
[Mozilla]: http://www.mozilla.org/
[HTML 4 Strict]: http://www.htmlhelp.com/tools/validator/doctype.html#html4strict
[HTML 4 Transitional]: http://www.htmlhelp.com/tools/validator/doctype.html#html4transitional
[XHTML 1.0]: http://www.w3.org/TR/xhtml1/
[HTML 4 Frameset]: http://www.htmlhelp.com/tools/validator/doctype.html#html4frameset
[HTML3.2]: http://www.htmlhelp.com/reference/wilbur/
[HTML4]: http://www.htmlhelp.com/reference/html40/
[HTML 2.0]: http://www.w3.org/MarkUp/html-spec/