Does anyone have a ballpark figure of how many people surf with style sheets off or browsers that are unable to see them (or even parts of them)?

I'm making a new site that uses css extensively, it'll be readable for non css browsers (the formatting is OK) but it looks *very* plain for them.

If I test in Opera and NS4.7, and it looks fine, should that be OK? What about WebTV? Does AOL see css differently? Any major things I should avoid?

Sorry for all the questions, but I'm just beginning to learn this stuff now and want to make sure I do it right.