Best FireFox Addons to Analyze Page Load Time

Google - Page Speed (from Google Webmaster Tools)
https://dl-ssl.google.com/page-speed/current/page-speed.xpi

Yahoo - YSlow
http://developer.yahoo.com/yslow/

http://www.searchenginejournal.com/best-firefox-addons-to-an...

Pingdom Tools
Test and Analyze your Page Load Time from another location
http://tools.pingdom.com/

Octagate SiteTimer
http://www.octagate.com/service/SiteTimer/

Web site speed test
http://www.websiteoptimization.com/services/analyze/

Page Load Time explained
...for many sites that reference dozens of external objects, the majority of the page load time is spent in separate HTTP requests for images, javascript, and stylesheets. AJAX probably could help, but speeding up or eliminating these separate HTTP requests might help more..
http://www.die.net/musings/page_load_time/

Performance Rules
Yahoo!'s Exceptional Performance team has identified 34 rules that affect web page performance. YSlow's web page analysis is based on the 22 of these 34 rules that are testable. These testable rules are listed below roughly in order of importance and effectiveness. Studies have shown that web page response time can be improved by 25% to 50% by following these rules.

1. Minimize HTTP Requests
2. Use a Content Delivery Network
3. Add an Expires or a Cache-Control Header
4. Gzip Components
5. Put StyleSheets at the Top
6. Put Scripts at the Bottom
7. Avoid CSS Expressions
8. Make JavaScript and CSS External
9. Reduce DNS Lookups
10. Minify JavaScript and CSS
11. Avoid Redirects
12. Remove Duplicate Scripts
13. Configure ETags
14. Make AJAX Cacheable
15. Use GET for AJAX Requests
16. Reduce the Number of DOM Elements
17. No 404s
18. Reduce Cookie Size
19. Use Cookie-Free Domains for Components
20. Avoid Filters
21. Do Not Scale Images in HTML
22. Make favicon.ico Small and Cacheable
http://developer.yahoo.com/yslow/help/index.html