If you’re running a vps (virtual private server), an oscommerce-based cart, a 3rd party google checkout payment module that requires zend optimizer and happen to be with a hosting company that offers ‘web site optimizations’ … (yeah I know, pretty select situation), make sure to take a close look at the web hosting control panel because ‘page speed optimization defaults’ may include the apache module mod_pagespeed, Google’s own bash at making your sites go faster.
A recent job I had was to fix a failing google checkout callback for a client who runs a site on a dreamhost vps. After a lot of of tests and removing various caching and compression features, plus an investigation into php compiled via fastcgi (that I wouldn’t recommend to anyone), I noticed that all the stylesheets were getting linked together in the page source code of the site. For example, a cre loaded site running product page tabs and a social media box might look:
Note ‘pagespeed’ in the url – this is an indicator that you too have google’s mod_pagespeed running on your server.
It was easy to deactivate the Page Speed Optimization module (which includes mod_pagespeed – remove a tick in a box) but man, it took some hunting down (mainly because I wasted time looking at the ‘complicated’ when it would be better to check the ‘obvious.’)
You can read a whole lot more about Google’s ‘Page Speed Optimization’ suite of tools (which includes the apache mod_pagespeed) from this url: code [dot] google [dot] com/speed/page-speed/
Here is a list of some of the filters it uses, to give you an idea of what it might do
to for your site: