Any browser with basic CSS support

IE6 and under
IE7
IE8
IE9

Firefox 1-3.0.19
Firefox 1-2.0.0.20
Firefox 3.5 up *

Safari 2.0-2.0.4
Safari 2.0-3.0.4 *
Safari 2.0-3.2.3 and Chrome up to 1.0.154.65 *
Safari 2.0-4.0 beta and Chrome up to 2.0.156.1 *
Safari 3.0-3.0.4 *
Safari 3.0-3.2.3 and Chrome up to 1.0.154.65 *
Safari 3.0-4.0 beta and Chrome up to 2.0.156.1 *
Safari 3.1-3.2.3 and Chrome 0.2.149.27-1.0.154.65 *
Safari 3.1-4.0 beta and Chrome 0.2.149.27-2.0.156.1
Safari 3.1+ and Chrome
Safari 4 beta up and Chrome 2+
Safari 3.1-4.0.3 and Chrome 0.2.149.27-5.0.375.29
Chrome 5.0.366.2-5.0.375.29
Safari 4.0.4+ and Chrome 5.0.366.2+
Safari 4.0.4+ and Chrome 5.0.396.0+

Konqueror 3.4-3.5.5
Konqueror 3.4-4.0.5
Konqueror 3.4-4.1.3
Konqueror 4.1-4.1.3 *
Konqueror 4.1-4.1.1 *
Konqueror 4.1.2-4.1.3 *
Konqueror 4.2+

Opera 7-8.54 *
Opera 7-7.54u2 *
Opera 7.2-9.27 *
Opera 7.2-8.54 *
Opera 7.2-7.54u2 *
Opera 9-9.27 *
Opera 9.5+
Opera 10+ *
Opera 10-10.1 *
Opera 10-10.5
Opera 10.5+
Opera 10.6+ *

* these rely on media-query hacks

More information is available at http://thomas.tanrei.ca/css-hacks.html