From, http://validator.w3.org/check?verbose=1&uri=http%3A%2F%2Flivetest.uberca...

there is no attribute "nowrap" ---> th nowrap="nowrap">Add to cart

and

there is no attribute "width" ---> td width="100%"

and

ID "edit-submit" already defined ---> input type="submit" name="op" id="edit-submit" value="Add to cart" class="form

and

ID "edit-nid" already defined ----> input type="hidden" name="nid" id="edit-nid" value="5"

you need to remove nowrap and width from the above and I think defining add to cart/submit buttons with "class" rather than "id" can solve the problem.

These are the main problem. I think if these are sorted out all the inner product pages will start to valid xhtml.