Page Speed: Firefox Add-on by Google to Optimize Websites for Faster Loading
Page Speed is a Firefox add-on released by Google to optimize your websites for faster loading. This add-on integrates with another add-on, Firebug, and is aimed at web developers trying to make their pages faster. It is basically a tool that will help you improve the loading performance of your website.
To use this add-on, once you installed Page Speed and restarted Firefox, expand Firebug and switch to the Page Speed tool tab. Move to your page, then click the Analyze Performance button. After a short loading time, you will see a list with all the factors that would make your site load faster, with an image illustrating whether or not your website checks for each.
Other Firefox plug-in are also available for the same purpose, but this one seems to be more robust. It checks for a wide range of optimization steps, including proxy caching, DNS lookups, CSS combination, JavaScript loading and parallel downloads.