Really, this is just a link to the MSDN article “How to Optimize a SharePoint 2007 Web Content Management Site for Performance“. Nice easy title.
To do so, open IIS Manager, and right click on the ‘Web Sites’ folder. Select the service tab, and check the check box. Don’t go for dynamic compression; this would be a bad idea.
You’ll also want to check/edit the file types compressed. See Using HTTP Compression for details, and you’ll probably need to add the .JS and .CSS extensions.
I must sit down and give this a proper test some time. Certainly I don’t see the same sizes in the article, but then I’m looking at the file sizes on disc; in 12 Hive, and in the temporary compression cache (typically %WinDir%/IIS Temprorary Compressed Files). My numbers show Core.js to be 575Kb uncompressed, 91Kb after compression. Nice!