Page Speed Extension for Firefox/Firebug

Page Speed is an open-source Firefox/Firebug Add-on. Webmasters and web developers can use Page Speed to evaluate the performance of their web pages and to get suggestions on how to improve them.
Page Speed performs several tests on a site's web server configuration and front-end code. These tests are based on a set of best practices known to enhance web page performance. Webmasters who run Page Speed on their pages get a set of scores for each page, as well as helpful suggestions on how to improve its performance.
With Page Speed, you can make your site faster, keep Internet users engaged with your site, reduce your bandwidth and hosting costs and improve the web!

Three steps to the Page Speed extension

Install

The Page Speed extension is now available as an extension to Mozilla Firefox. It runs in the popular Firebug web development tool. Downloading the Page Speed extension requires that you have both Firefox and Firebug installed and running.
Page Speed is downloadable and as all Firefox extensions, checks for updates at restarts of Firefox. If an update is available, Firefox will give you the option of downloading the newer version of Page Speed to get the latest updates to the rules and functionality that is added by the community.
In Mozilla Firefox 3.6, you can access the add-on by going to the Tools menu, then navigate to Add-ons.

Run Page Speed against your web pages

Follow the instructions provided to start Page Speed in Firefox/Firebug. When you visit a web page, run "Analyze Performance" against that page. Page Speed will present you with a set of rules and recommendations. Before you start changing the scripts and resources on your pages, press on the rule to understand what it is pointing out and its background.
Get familiar with the tool. There are a number of features that are easily accessible from the menus of the extension. In particular, in the top tab called "Page Speed", a caret next to the text gives you the ability to set preferences for how Page Speed runs and where it saves optimized resources.

Learn more about Web Performance

The field of web performance is a complex space. While there are many interesting books, blog posts and discussion forums, we provide here a set of pages related to web performance and organize it in terms of contribution to the speed of a web page, whether by serving less bytes -through better compression or caching-, minimizing round-trips and optimizing the order of resource download for the browser.
This documentation is by no means complete or final. We update it regularly with new rules and updates to how the rules apply to modern browsers.