in lower case</a></h2>

<p>XHTML documents must use lower case for all HTML element and
attribute names. This difference is necessary because XML is
case-sensitive e.g. &lt;li&gt; and &lt;LI&gt; are different
tags.</p>

<h2><a name="h-4.3" id="h-4.3">4.3 For non-empty elements,
end tags are required</a></h2>

<p>In SGML-based HTML 4.0 certain elements were permitted to omit
the end tag; with the elements that followed implying closure.
This omission is not permitted in XML-based XHTML. All elements
other th