• go moodle 2 home page
• be sure the "Main menu" is part of the page
• turn editing on
• check for compliance with xhtml strict
  you will find three times the same error.

1. the "Main menu"->"Add a resource" drop down menu,
2. the "Main menu"->"Add an activity" drop down menu,
3. the "Add a block" (pseudo block)->"Add..." drop down menu,
are followed by a:
<noscript style="inline"><input type="submit" value="Go" /></noscript>

This last line breaks xhtml strict.
It should be, at least,
<noscript style="inline"><div><input type="submit" value="Go" /></div></noscript>

To be a real ball breaker, even style="inline" should be changed to a class call.