Do you include support of IE6 in your layout scripts? For example transparent PNG fixes and other stuff like this related to IE6.
I never create browser specific CSS rules that modify the layout... The only time I provide CSS rules that are unique to certain browsers is to further enhance user experience. ie. Opacity, border radius, transparent pngs etc.
I don't design for IE6 at all, it's wayyyy to old. Trying to support as many browsers as possible will just drive you nuts.
The way I figure it, people that are still dumb enough to use IE6 probably don't care about aesthetics.