This page is valid HTML 4.01 Strict!
...Or, rather, it was valid HTML 4.01 Strict.
Then Drupal got to it, and decided to make it invalid HTML/XHTML Nonstandard Random Useless Crap.
Namely, Drupal has decided to do the "Fake Empty Element" dance. That's where valid HTML tags, like "
<link>," are turned into invalid HTML tags like "
Such a tag would be valid XML and therefore (might) be valid XHTML.
But this page doesn't use XHTML for a few very simple reasons: