So I started tweaking the html/css of this page. Nothing fancy as far as I can see.
Now it looks completely wrong in Firefox (see for yourself) and fine in every other browser I can think of. The html has been validated by the W3 tool. I am mystified, has anyone ever come across this before?
You just need to clear the floats. Try adding this to your stylesheet:
table.layouttbl
{
clear: both;
}