According to Wired,

  • The target for CSS support in IE8 is full and complete support for CSS2.1.
  • The only CSS3 module in IE8 is writing-mode (for vertical text support). IE has supported this since version 5.x, so it will continue to do so.
  • IE8 will not support CSS' border-radius, which is often used to make rounded corners without images. Microsoft's Chris Wilson confirms that border-radius support is "high on the wish list," though, and should make its way into the next release after IE8.

Full CSS 2.1 complete support is cool but it must be said that "full CSS 2.1 support" does not mean anything yet. CSS 2.1 is not yet a W3C Recommendation and it does not have an approved full Test Suite yet. Microsoft has submitted a rough 7,000 CSS 2.1 tests to the CSS WG but these tests need review before becoming official.

I am a bit surprised that Selectors are not fully or almost fully implemented in IE8. IE8 will then be far from Gecko, Opera and Webkit in terms of Selectors. Keeping a too low level on Selectors is a door open to CSS hacks based on selectors' sniffing, and that's a true disappointment to me.