The poster doesn't mention this, but there are (sometimes) good reasons for doing OS-specific re-directs, but not for browser rendering reasons (shame on anyone who does that these days. In a world of nearly standards compliant browsers I'm hoping the days of browser detects are over). If you've got a Windows product and a Mac product why not direct your users to the appropriate version? Netscape does this when you go to download the latest version of Navigator... they do an OS-detect and show you the Mac version for download if you come in on a Mac, and the Windows version if you come in on Windows. Pretty clever, actually. :-)