Browser specific hacks - css filters

Webkit only css hack (safari, chrome):

@media screen and (-webkit-min-device-pixel-ratio:0) {

body{ background:red}

}

Firefox only css hack:

@-moz-document url-prefix() {

body{ background:green}

}

Opera only css hack:

@media all and (-webkit-min-device-pixel-ratio:10000), not all and (-webkit-min-device-pixel-ratio:0) {
       body {background:orange}
 }

IE only css hack:

body { 
 background : green\9; /* IE9,IE8 and below */ 
 *background : yellow; /* IE7 and below */ 
 _background : orange; /* IE6 */ 
}

More:

http://css-tricks.com/snippets/css/css-hacks-targeting-firefox/
http://www.evotech.net/blog/2007/04/ie7-only-css-hacks/