Addicted to YSlow and what Jawr can do to help

At the No Fluff Just Stuff (NFJS) conference I attended 2 weeks ago, somebody mentioned YSlow, which is a tool for analyzing websites in regards to performance and is a plugin for Firebug. Hence, this week I spent some time using it and fixing the issues YSlow found on my project.

It is really nice and almost addictive...YSlow grades the performance of your website in a number of categories. There is a good site at yahoo explaining those categories called: "Best Practices for Speeding Up Your Web Site".

For example, you should always put CSS at the top of your web pages and JavaScript files should be at the bottom. While this is easy to fix, the recommendation to reduce HTTP request is a bit trickier to fix.

Well, let's assume you implemented a typical Web 2.0 website using a few Javascript libraries such as Prototype, Scriptaculous as well as your own Javascript files. Furthermore, you broke your CSS into multiple files because otherwise you would simply lose control over it entirely.

That of course causes a lot of HTTP requests when loading the files and thus leads to a degradation of your website's performance.

But luckily if you write Java based web applications there is a really cool library out there called Jawr that let's you bundle up (combine) your Javascript and CSS files. Not only that, Jawr also minifies your Javascript and CSS files plus it is able to GZip the files as well. Jawr also provides a nice quickstart tutorial and lastly Jawr also has a tutorial that explains how to use it with the big JavaScript libraries such as jQuery, Prototype, Scriptaculous and Yahoo! UI library.