I haven't been tempted to do anything adventurous in CSS for a couple of years, so new developments in browsers have largely passed me by. But rumor tells me that the more widely used versions of MSIE are actually pretty good. I can live without the "turned-up corners" effect of the menu in http://www.w3.org/Style/CSS/ but, corners aside, does this kind of thing either display as intended or at least degrade gracefully on MSIE version, um, er, I suppose 6+?

Actually I was thinking of a smaller, translucent version of W3C's menu. I can write it and test it, and I can eventually commandeer some Doze computers and test it on that too; but some general pointers on what not to bother attempting would be welcome.

I found that MSIE 6 is reasonably competent, although still buggy. There are "standard hacks" to work around the bugs. My personal site uses the "zoom: 1" hack to keep MSIE 6 from making a mess of the layout.

I can't test with MSIE 5.x (my tax software upgraded my system automatically a couple years ago), but its market share is pretty small now. And I can't test with MSIE 7 (it won't run on Win/ME), but I've heard that it doesn't butcher things any worse than MSIE 6.

But YMMV, depending on what you want to do with CSS.

Did you say menus in CSS? Not sure if there's a translucent one amongst that lot, but odds are with it.
http://www.cssplay.co.uk/menus/

IE 7.0 isn't too bad, to be honest. Not on the same page as Gecko, Opera or Safari, but that's to be expected, but it does approach decent CSS support.

It certainly is much better than IE 6.0, that's for sure.