In XHTML, the HEAD section is mandatory. Here is our XHTML document so far:
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"DTD/xhtml1-transitional.dtd">
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You will also notice that ALL tags, with the exception of the !DOCTYPE tag, are in lower case. This follows the XML convention, as tags are case-sensitive in XML. The TITLE tag is also mandatory in XHTML. Because all tags must have end tags, if you want to include tags like META or LINK, which normally do not have end tags in HTML, must have either the corresponding end tag in XHTML (like /meta or /link), or must end in />.