Further to Ross' answer, you can only target the Internet Explorer rendering engine with conditional comments; there is no similar construct for other browsers. For example, you can't write conditional comments that target Firefox, but are ignored by Internet Explorer.
The way I achieve the same effect as your example above is to sniff the user agent string. I then deliver a suitable CSS file for that browser. This isn't perfect because sometimes people change their user-agent string for compatibility.
The other way to target different browsers is to utilise browser specific hacks. These are particularly nasty because they usually rely on bugs in the browser and bugs are liable to be fixed!
User-agent sniffing is the best all-round solution in my opinion.