The tag is fully supported of course. It is just to indicate that it is an unordered list after all. Correct syntax would be something like this:
Code:
<ul>
<li>first list item</li>
<li>second list item</li>
<li>third list item</li>
</ul>
As you can see, the list items must be enclosed in the <ul></ul> tags. Also, don't forget to close the list items. I know that HTML gets away with it, as the renderers close it for you, but XHTML is more strict.