How many CSS hacks are necessary because a browser acknowledges support for something or doesn't support something versus having a totally broken implementation

How many CSS hacks are necessary because a browser acknowledges support for something or doesn't support something versus having a totally broken implementation of something? In otherwords, this wouldn't fix at all being able to conditionnally choose CSS for IE's busted hasLayout oddity, nor would it allow non-hacky CSS to work around different box models, because we didn't even have names for these things when they were discovered and parsing bugs were discovered to allow some browsers to see the rules and others not to.