There is general advice here:-
http://w ww.wickham43.net/specialeffects.php#highlightedlinks

which shows how the whole of a div can be clickable, not just the text. If you cannot do this directly with a table td tag, then put a div inside the td tag with the same width and height and follow the code to make the whole area clickable. The page above has the three columns of links at the top of the page also clickable for the whole width with a different background color, instead of just the text clickable.