This is the final problem I have with my site. It now works exactly how I want it in every browser, except Firefox 3.0.##. (Also haven’t tested IE6).
It looks fine in every browser, but in FF 3.0 it looks like padding: 4px 0 4px 0; is added to the menu. I was playing around with the paddings and found out that is not where the problem lies, because it’s not padding that is added. I also tried changing the line-height (to 1.2em), that almost worked but it isn’t the solution, there is still a 1px difference between 3.0 & 3.5 that becomes very apparent because of the menu item hover effect.