I was doing some design stuff today and i had issue with browser compatibility.
When i use e.g
border-top:1px solid #aaa;
It works in FireFox and IE8 and above but couldn't get it to work with IE7.
It was driving me nuts!!!
But i came out with a solution and by adding
display: inline-block;
vertical-align : bottom;
It did the trick.
Hope that helps