the doctype being used on your page:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
is the XHTML 1.0 Transitional doctype.
in the XHTML 1.0 Transitional doctype, all html tags must be in lower case.
instead of:
<UL>
<LI> ... Level one, number one...</LI>
</UL>
it should be:
<ul>
<li> ... Level one, number one...</li>
</ul>