Conditional CSS is a server side script which allows you to target particular browsers within your CSS files. The script detects a visitor’s browser and then parses your css files, removing the conditional statements and any lines that aren’t meant to go to that browser. I think I like this more than traditional browser filters but less than using conditional comments to serve an extra stylesheet with overrides to Internet Explorer. I haven’t tested it to determine how much of an issue the additional processing overhead is, so I’m not sure how usable it is. It’s an interesting technology and is available for multiple platforms including PHP and C. The C version is apparently very fast.