If your clients use just IE 5+ (usually enterprise application) use GZIP to reduce network traffic.

Internet explorer from version 5+ can recognize GZIP encoding streams, open them and render the "unziped" HTML. So if all of your clients use just IE 5+ you can take advantage of this ability to reduce network traffic. This practice is very usable for national spread organization that include sites with low bandwidth lines (GZIP can reduce stream size up to 10 times). To use this ability you need to ZIP all streams  leaving your IIS server. HttpModules save our day by enable us to track down every outgoing response. Ben Lowery (our hero) create HTTPModule that Zip every outgoing request from the server. You can download the module with source code, explanations and sample from Bens site :  http://www.blowery.org/code/HttpCompressionModule_1.1.zip