This is my first attempt at building a theme, for which I have used the default and one other as a rough 'guide' template, to get used to the css class and ID structures.
I managed to build it with little problem using IE7 and XAMPP on my home PC. However, at university (where I use both IE6 and Firefox) I noticed several discrepencies in the layout. Fortunately all but one has now been resolved.
My problem lies in the fact I'm using a double border with nested divs. In Firefox, text further down the page 'overflows' the main content. I'm unsure exactly why this is.