Re: [CSS21] Test Suite

>    IE does support PNG, except for alpha transparancy.

I do not know if it matters for the test suite in question, but IE also
handles gamma correction differently than other browsers.  For example, a
fully opaque PNG image may differ from the CSS-specified color of a
surrounding page.

I do not know all of the details off the top of my head, but here is a page
that seems to give a decent overview of the issue:

http://www.hut.fi/u/hsivonen/png-gamma.html