Query for those of you who know about CSS.

Why doesn’t the right-hand menu in http://www.aquarionics.com/tempstuff/menu.html work?

By this I mean it’s supposed to look like it does in http://www.aquarionics.com/tempstuff/aquarionics3.5.jpg, and works fine in ie, but in Opera & Moz there is a one line gap between the top and content and another between the content and tail. What is even more odd is that if I put a border around the content (commented in the code) the gap vanishes in Opera, and reduces to a couple of pixels in Moz.

Anyone got an idea?