madhubala772: A doctype declaration

Friday, 2 March 2012

A doctype declaration

A doctype declaration refers to the rules for the markup language, so that the browsers render the content correctly.

Example

An HTML document with a doctype of HTML 4.01 Transitional:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<title>Title of the document</title>
</head>

<body>
The content of the document......
</body>

</html>

HTML Different Doctypes

The doctype declaration is not an HTML 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.

The doctype declaration should be the very first thing in an HTML document, before the <html> tag.

Tip: Always add a doctype to your pages. This helps the browsers to render the page correctly!

HTML 4.01 Strict

This DTD contains all HTML elements and attributes, but does NOT INCLUDE presentational or deprecated elements (like font and center). Framesets are not allowed:

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

HTML 4.01 Transitional

This DTD contains all HTML elements and attributes, INCLUDING presentational and deprecated elements (like font). Framesets are not allowed:

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

HTML 4.01 Frameset

This DTD is equal to HTML 4.01 Transitional, but allows the use of frameset content:

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

Tips and Notes

Look at our table of all HTML/XHTML elements, and which DTD each element appears in.

Use W3C's Validator to check that you have written a valid HTML/XHTML document!

HTML DOCTYPE Element

Tag	Description
<!DOCTYPE>	Defines the document type. This declaration goes before the <html> start tag

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