YSlow analyzes web pages and tells you why they’re slow based on the rules for high performance web sites. YSlow is a Firefox add-on integrated with the popular Firebug web development tool. YSlow gives you:
* Performance report card
* HTTP/HTML summary
* List of components in the page
* Tools including JSLint
If you do any site development this is well worth getting. I found how my sites were performing and what was slowing them down. I have not had time to implement changes yet, but look forward to seeing how much I can speed up my site reponse time.