Compression saves on bandwidth.  It doesn't always mean that the page loads faster.  It takes some time for the server to compress the file, and some time for the client to decompress it.  If your bandwidth is really low (dialup) then compression would save time because the computer is faster than the connection.  With higher bandwidth like cable and DSL, it could actually be slower to use compression.

I can't tell you how much of a benefit/trade-off there is for html compression.  My experience with real-time compression is mostly with VoIP and SCP file transfers. 

I do know that we recently enabled html compression at work and we are seeing an increase in HTTP 500 errors (which is an "Internal server error"  ..very specific.)

Apache isn't really black magic.  It is fairly straight-forward.  It probably seems complicated because it has lots of options and can be extended by a large number of modules.  Fortunately, the configuration is also modular and stored in a *nearly* human readable text file.  The configuration files often even come with self-documenting comments.  So, it looks big and complicated at first, but it starts to make sense once you dig in and play with it a little.

Thanks, bro.

I will watch for 500 server errors. Haven't noticed any errors yet. (mod_deflate compiled/enabled; as mod_gzip doesn't work with Apache 2.x)

Rad wrote on Sep 29^th, 2008 at 4:45pm:

Don't try. It's a small and potentially useful part of the performance puzzle, but only a small part. And there are parts you should compress, but for most things it's not important.

I'd suggest you go with YSlow's analysis first, because that makes much smarter suggestions than that website does. Yahoo's guidelines are excellent, and read their blog entries too.

Compression is a distant second best behind really good cache control - setting Expires: headers appropriately, for instance. And where compression matters most are for page elements like external CSS and scripts that can block the page being rendered ahead until they are loaded, not for the content itself. You definitely should minify any Javascript and set it to be gzipped (after setting up Expires: headers, mind you) and that will typically be the only thing that really matters to the final end-user perception of page loading, because your main goal is to start the page rendering quickly. How things load after that isn't nearly as important.