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XHTML file type declaration

Author：Eve Cole Update Time：2025-04-06 17:48:02
XHTML defines three file type declarations.

The most commonly used is XHTML Transitional.

<!DOCTYPE> is used for compulsory use.

An XHTML document has three main parts:

  • DOCTYPE
  • Head
  • Body

The basic document structure is as follows:

 <!DOCTYPE ...><html><head><title>... </title></head><body> ... </body></html>

In an XHTML document, the document type declaration is always on the first line.

An instance of XHTML

This is a simple (minimized) XHTML document:

 <!DOCTYPE htmlPUBLIC -//W3C//DTD XHTML 1.0 Strict//ENhttp://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd><html><head><title>simple document</title></head><body><p>a simple paragraph</p></body></html>

Document type declaration defines the type of the document:

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

The rest of the document is similar to HTML:

 <html><head><title>simple document</title></head><body><p>a simple paragraph</p></body></html>

3 document type declarations

  • DTD specifies the syntax of web pages using the Common Markup Language (SGML).
  • Common markup language applications such as HTML use DTD to specify rules applied to tags in a particular document, including a series of declarations of elements and entities.
  • In a document type declaration or DTD of a General Markup Language (SGML), XHTML is specifically described.
  • XHTML DTD uses precise computer-readable language to describe the syntax and syntax of legitimate XHTML tags.

There are three types of XHTML document:

  • STRICT (Strict Type)
  • TRANSITIONAL (Transition Type)
  • FRAMESET (frame type)

Three XML document types for XHTML 1.0

XHTML 1.0 specifies three XML document types to correspond to the above three DTDs.

XHTML 1.0 Strict

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

Use in such cases: Clean marking is required to avoid performance confusion. Please use it with the cascading style sheet.

XHTML 1.0 Transitional

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

Use in such cases: when it is necessary to take advantage of the performance characteristics of HTML, and when it is necessary to write XHTML for those browsers that do not support cascading style sheets.

XHTML 1.0 Frameset

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

In such cases, when using HTML frameworks, you need to split the browser window into two or more frames. 2 pages in total Previous page 12 Next page

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