The Exclamation Invalid Filter

Or, the WebKit Build 85 Stiletto

This should be green not red

It is green in:

• Mozilla (0.92, 0.94, 1.0, 1.01, 1.4, 1.6 versions tested)
• Camino 0.7
• Safari 1.2 (WebCore build 125)
• Safari 1.0.1 (WebCore build 85.6)
• iCab 2.9.7
• IE 6.0 Windows
• IE 5.5 Windows
• IE 5.0 Windows (but only with the comment hack included)
• IE 4.0 Windows (but only with the comment hack included)
• IE 5.2.3 (Mac OS X)
• IE 5.0 (Mac OS 9)
• IE 4.5 (Mac OS 9)
• IE 4.01 (Mac OS 9)
• Opera 7.x (Windows)
• Opera 6 (OS X and Windows)
• Opera 5 (OS X and Windows)
• Opera 3.5 (Windows)
• Netscape 7.0&endash;7.1
• Netscape 6.x
• Netscape 4.77 (OS 9)
• Netscape 4.61 (OS 9)
• Netscape 4.04 (OS 9)

It is red in:

• OmniWeb 4.5 (presumably also Safari 1.0)
• OmniWeb 5.0 beta (using WebKit build 85)

The CSS used is:

p.thing {color:green;}
.doofus ! p.thing/**/ {color:red;}

It is based on one of the tests of forward-compatible parsing in the W3C CSS1 Test Suite, combined with a comment that hides the second rule from IE 4.0 and 5.0 for Windows. It is not valid according to the W3C CSS validator, as the exclamation point in not a recognised operator in any current version of CSS. Thanks to Tony Leggett and Chris Nott for testing.