At work, I’ve started to test stuff in IE7 in addition to Firefox and IE6; this has forced me to figure out how to pass certain CSS rules to all versions of IE and nothing else. (Virtually all known CSS hacks for IE have been fixed in version 7.) I know conditional comments are usually the way to go, but what if you need to override just one or two rules? Not worth the trouble of creating a separate stylesheet, in my opinion. After some hunting around just now, I realized that IE’s expression property is what I want: instead of postion: relative; one can do position: expression('relative');. Tell your friends!