stylesheet.css contols the warnings & some navigator stuff

stylesheet_tm.css controls the header and footer boxes, menu boxes, and ezpage boxes, products boxes.

stylesheet_boxes controls the layout of the sideboxes.

stylesheet_main contols category, shopping cart, shipping estimator, etc.

I didn't write it, it was a template that was used. I can manipulate the properties in the stylesheet_tm file for the menu boxes and see changes so I know that's the right area. it's just odd that the last one falls off. In the above quote I showed all the code connected to the menu box.

What's odd is it looks fine in some browsers, but not others. So, to answer your question, yes, I'm aware of what these files control.