XHTML DTD

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The most common DTD is XHTML Transitional.

<!DOCTYPE> Is Mandatory

An XHTML document consists of three main parts:

  • the DOCTYPE declaration
  • the <head> section
  • the <body> section

The basic document structure is:

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

Note: The DOCTYPE declaration is always the first line in an XHTML document

An XHTML Example

A simple (minimal) XHTML document:


<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html>
<head>
<title>simple document</title>
</head>
<body>
<p>a simple paragraph</p>
</body>
</html>

The DOCTYPE declaration above defines the document type. The rest of the document looks like HTML.

Document Type Definitions (DTD)

  • A DTD specifies the syntax of a web page in SGML
  • DTDs are used by SGML applications, such as HTML, to specify rules for documents of a particular type, including a set of elements and entity declarations
  • An XHTML DTD describes in precise, computer-readable language, the allowed syntax of XHTML markup

There are three XHTML DTDs:

  • STRICT
  • TRANSITIONAL
  • FRAMESET

XHTML 1.0 Strict

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

Use the strict DOCTYPE when you want really clean markup, free of presentational clutter. Use it together with CSS.

XHTML 1.0 Transitional

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

Use the transitional DOCTYPE when you want to still use HTML's presentational features.

XHTML 1.0 Frameset

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

Use the frameset DOCTYPE when you want to use HTML frames.


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