I had a chance to work a bit with a new page speed and JS mimification tool from google and i have to say its really cool.

The tool i am talking about is closure compiler and page speed and you can find it here

Web performance is not all about database calls and PHP speed. Its also about how many elements you have to be downloaded, in what order, how big are they, can they be cached, can they be compressed etc. Page speed helps you to figure out how to speed up the loading time not the html generation time. Pages consist of many js, css files as well as images. Knowing what causes delays is crucial to successful website performance optimization.

Page speed installs itself as a plugin for the firebug in firefox. Once its installed it will add a few new tabs and set of new options to help you debug performance issues you have with your site.

Its similar to Yahoo "yslow" which you can find here. In my opinion its a bit cooler though : ) It shows you suggested compression gains as well as suggested caching improvements, file sizes and js/css bundling.

Once you play around with both yslow and page speed you will be able to optimize performance of your sites. You will be able to fix missing caching headers to make page elements cache better. you will be suggested how to setup content delivery network or spread load across multiple domains. You will see how much time can be gained by compressing and combining javascript and css files into bigger bundles.

In general you will be able to speed up the load time of your pages significantly.

Its also a great resource to learn what is important and how does it affect the performance of your website. Analysis of a few projects will help you making better design decisions in the future :)

Again, great resource of knowledge for any web developer! i really recommend it.