IE borders breaking navigation

Answer 1

Try getting rid of the height rule on the anchor tags, and using top/bottom margins/paddings to ensure they fill the space. I find CSS using floats a lot easier when you don't try to enforce heights on elements.

Answer 2

It's not the borders doing it - it's the line-height. Your nav anchors are inheriting "line-height: 2em" from #header. Try setting the line height on the anchors (or their parent LI's or the UL) to something smaller - maybe 1.5em or so - and then make up the difference with some top padding on the anchors