Page Speed is a Firefox add-on (integrated with Firebug), which has been using to improve the performance of web pages at Google. This is very, very useful tool for web developers.
When you run Page Speed, you get immediate suggestions on how you can change your web pages to improve their speed. For example, Page Speed automatically optimizes images for you, giving you a compressed image that you can use immediately on your web site. It also identifies issues such as JavaScript and CSS loaded by your page that wasn’t actually used to display the page, which can help reduce time your users spend waiting for the page to download and display.
You can download and install Page Speed at here
