W3C DOCTYPEs and Validation

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DTDs - Document Type Definitions

A valid HTML/XHTML document declares what version of HTML/XHTML is used in the document. The document type declaration names the document type definition (DTD) in use for the document.


HTML 4.01 Strict, Transitional, Frameset

HTML 4.01 specifies three DTDs, so authors must include one of the following document type declarations in their documents. The DTDs vary in the elements they support.

  1. Strict DTD
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
  2. Transitional DTD
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
  3. Frameset DTD
    <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Frameset//EN" "http://www.w3.org/TR/html4/frameset.dtd">

XHTML 1.0 Strict, Transitional, Frameset

XHTML 1.0 specifies three DTDs, so authors must include one of the following document type declarations in their documents. The DTDs vary in the elements they support.

  1. Strict DTD
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
  2. Transitional DTD
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
  3. Frameset DTD
    <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Frameset//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-frameset.dtd">

XHTML 1.1 DTD

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

For more information on DOCTYPEs, their usage and formatting, visit these resources...

  1. The Global Structure of an HTML Document - W3C
  2. DOCTYPE Declaration in Documents - Complete Listing of DTDs - W3C
  3. Fixing your site with the right DOCTYPE - A List Apart

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Last modified: 2010-10-02T09:39:30-0700


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