Tim Bray lays the blame in the big CSS debate where it should be:
The problem isn’t that CSS is too hard. The problem isn’t browser incompatibilities in general. The problem is specifically that Microsoft Internet Explorer is a mouldering, out-of-date, amateurish, out-of-date pile of dung. Did I say it’s out-of-date?
He also brings up a good optimistic point. The percentage of Internet Explorer users is probably not going to get any higher, and other browsers can only go up from here.
No it's not, I write this using IE 5.0... :P