 B. Element
Prohibitions</a></li>

<li class="tocline"><a href="#guidelines">Appendix C. HTML Compatibility Guidelines</a></li>

<li class="tocline"><a href="#acks">Appendix D. Acknowledgements</a></li>

<li class="tocline"><a href="#refs">Appendix E. References</a></li>
</ul>
</div>

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<h1><a name="xhtml" id="xhtml">1. What is XHTML?</a></h1>

<p>XHTML is a family of current and future document types and modules that
reproduce, subset, and extend HTML 4.0 <a href="#ref-html4">[HTML]</a>. XHTML