After some extensive testing, I can report that ie5 for Mac appears to be Microsoft's first CSS1 compliant browser.

Using W3C's CSS Test Suite, the only property in the CSS standard not supported by ie5 is text decoration: blink, which is not only ugly as sin, but a non-mandatory property.

ie5 for Mac even passed the CSS Acid Test, which previous standards compliant MS browsers failed.

However, House of Style reports that there are still bugs in the support of the vertical-align text property and some of the inline elements.

I also notice that as ie5 uses a highlight box for active links, rather than the ALINK colour, this could also be seen to be broken.

Finally, as previously commented on evolt, MS have seen fit to break the 72dpi screen resolution standard on Macs, just as they have previously for all Windows applications. While it is resettable via user preferences, it is still a regrettable backward move portrayed as progress.