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HTML & XHTML: The Definitive Guide, 6th Edition by Bill Kennedy, Chuck Musciano

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Appendix D. The HTML 4.01 DTD

The HTML 4.01 standard is formally defined as three Standard Generalized Markup Language (SGML) Document Type Definitions (DTDs): the Strict DTD, the Transitional DTD, and the Frameset DTD. The Strict DTD defines only those elements that are not deprecated in the 4.0 standard. Ideally, everyone would create HTML documents that conform to the Strict DTD. The Transitional DTD includes all those deprecated elements and more accurately reflects the HTML in use today, with many older elements still in common use. The Frameset DTD is identical to the Transitional DTD, with the exception that the document <body> is replaced by the <frameset> tag.

Since the Transitional DTD provides the broadest coverage of all HTML elements currently in use, it is the DTD upon which this book is based and the one we reproduce here. Note that we have reprinted this DTD verbatim and have not attempted to add extensions to it. Where our description and the DTD deviate, assume the DTD is correct:

<!-- This is the HTML 4.01 Transitional DTD, which includes presentation attributes and elements that W3C expects to phase out as support for style sheets matures. Authors should use the Strict DTD when possible, but may use the Transitional DTD when support for presentation attributes and elements is required. HTML 4 includes mechanisms for style sheets, scripting, embedding objects, improved support for right to left and mixed direction text, and enhancements to forms for improved accessibility ...

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