Google has released an Apache module which attempts to speed up web pages.
I am testing mod_pagespeed right now.
I have noticed two problems so far. I had to add this to /etc/apache2/mods-enabled/pagespeed.conf to enable the CSS on one of my Joomla sites to load properly:
It looks like this could have significant benefits and significant risks. Tuning the filters could be long and testing could be arduous.
# Disable problem filters
I added this a few weeks to a server of mine and the css quit being displayed on a few sites. I quickly turned it off and haven't looked back. Maybe in the future I'll look at it again.
We had a new error. mod_pagespeed was storing lock files as directories in /var/mod_pagespeed/files/. It quickly grew to more than 32,000 directories, which hit a limitation imposed by the ext3 filesystem. This caused mod_pagespeed to starting filling up apache's error log -- to the tune of 60GB of error messages. This broke Apache.
I had to disable mod_pagespeed. I filed an issue report here.