Thanks for this list — I've been wondering about using Opentype features in CSS. Could you point to or provide a few code snippets demonstrating the use of these properties?

It's worth noting that the typography properties themselves are at a higher level than the OTL features, i.e. the latter represent one possible way of implementing a CSS3 typography property; the same property could also be implemented with equivalent e.g. AAT or Graphite features.

I note that there doesn't seem to be support for caps as smallcaps (OTL=c2sc), which is a problem. This is probably a distinction that needs to be made at the caps-value level. [The same is true for caps as petite-caps, of course.]

Yes, the CSS properties merely correspond to OpenType. They could correspond to other implementations. In practice, will they, though?

Now, since I’m one of those people who does not sit down to read the OpenType specification over coffee, which is odd because I have done exactly that with many other specifications, do please explain, John, if c2sc means “every single letter becomes small caps, whether originally capitalized or not.”

Do you know if they will get the number weights to correspond to fonts?

example:
font-weight:300;

You know how they have 100, 200, 300, ..., 900

Then again I'm not sure what the fonts have to do, to be able to do that. Would be interesting to find out.

see: http://dev.w3.org/csswg/css3-fonts/#descdef-font-weight

Joe, c2sc converts uppercase letters (and potentially lining figures and some punctuation) to smallcaps, and smcp converts lowercase letters to smallcaps. Practically, c2sc isn't expected to be applied independently of smcp, so I would expect the CSS3 caps-value to have options similar to InDesign's smallcaps (smcp) and all-to-smallcaps (c2sc+smcp) distinction.