I get sick of all the ACID, ACID, ACID clammoring. A benchmark, not a priority -- and by no means the true measure of a browser--not yet, anyway.
-allen
I have mixed feelings on Acid2 myself. Yes, it has been misrepresented in what it is supposed to achieve, and supporting it will not make cross-browser dev headaches go away completely.
But it really does test a series a fundamental building blocks that have never been properly addressed. Of course web devs have been hacking round browser bugs since the WWW was born. The IE 7 team has tried to fix all the glaring bugs in existing things it breaks (which is good[1]), and simply cannot address the changes Acid2 requires. Neither can Mozilla till the gecko core gets a serious reworking. It took Opera a year to implement its fixes.
Though the test itself looks "dumb", the techniques behind it aren't - solid positioning, min/max-width/height, generated content, CSS tables and others would make a clear difference in what web developers can achieve, and what users would experience. That is important for accesibility and many other things...
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[1] I DO welcome IE7 - anything that is less of a buggy mess that IE6 was is warmly greeted!