I've been having trouble with the main and sidebar divs, which have been spilling over the bottom of the containing table, when viewed in Firefox. Even when I set the height of the table to auto. However, the problem seemed to fix itself once I refreshed the page. So I thought it must have been the way Firefox is loading the content when the information first arrives. After about two hours of smashing my head against the keyboard, I noticed that when the page is loaded the text would appear first and then expand to accommodate the images, but the table wouldn't.

I managed to fix the problem by defining the image size in the img tag. I think the browser takes that information and makes room for the image before the image actually arrives. I could be totally wrong, but it works anyway.