CreateSites: XHTML Doctypes

Monday, July 4, 2011

XHTML Doctypes

<!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 refers to a Document Type Definition (DTD). A DTD specifies the rules for the markup language, so that the browsers render the content correctly.

An XHTML Example

The example below shows an XHTML document with a minimum of required tags:

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

<html xmlns="http://www.w3.org/1999/xhtml">

<head>
<title>Title of document</title>
</head>

<body>
</body>

</html>

Note: The xmlns attribute in <html>, specifies the xml namespace for a document, and is required in XHTML documents.

XHTML Different Doctypes

The <!DOCTYPE> declaration is the very first thing in an XHTML document, before the <html> tag.
The <!DOCTYPE> declaration is not an XHTML tag; it is an instruction to the web browser about what version of the markup language the page is written in.
The <!DOCTYPE> declaration refers to a Document Type Definition (DTD). The DTD specifies the rules for the markup language, so that the browsers render the content correctly.

XHTML 1.0 Strict

This DTD contains all HTML elements and attributes, but does NOT INCLUDE presentational or deprecated elements (like font). Framesets are not allowed. The markup must also be written as well-formed XML.

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

XHTML 1.0 Transitional

This DTD contains all HTML elements and attributes, INCLUDING presentational and deprecated elements (like font). Framesets are not allowed. The markup must also be written as well-formed XML.

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

XHTML 1.0 Frameset

This DTD is equal to XHTML 1.0 Transitional, but allows the use of frameset content.

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

XHTML 1.1

This DTD is equal to XHTML 1.0 Strict, but allows you to add modules (for example to provide ruby support for East-Asian languages).

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">