Internet Explorer 7

You’ve probably read more reviews on this browser than you want to do but this one could be different. Microsoft promised a more ’standards compliant’ browser (Not before time either!) In the end though this never happened. IE7 supports around 52% CSS2 and around the same percentage for XHTML.
This might be fine for the general users who just look at existing websites but for the designers its a nightmare having to hack CSS for IE6 + IE7 just so the website renders correctly is going to cause more and more hassle.