CSS can be so frustrating sometimes! Took me forever to hunt down some hidden spacing in my divs, was a result of IE overriding my specified <hr /> height.  Once i figured out IE and my <hr /> tag was the culprit a quick google search gave me a couple solutions.

IE doesn’t seem to allow <hr /> elements to be sized smaller than the font size. Nothing I tried worked,  so now i just use a bottom or top border of 1px on my divs. This was suggested to have the most cross browser consistency. I’ve sworn them (hr tags) off altogether.