Web Performance Best Practices and Rules

Yahoo!'s Exceptional Performance team has identified 34 rules that affect web page performance. YSlow's web page analysis is based on the 23 of these 34 rules that are testable. Click each performance rule below to see the details.

1. Minimize HTTP Requests

2. Use a Content Delivery Network

3. Avoid empty src or href

4. Add an Expires or a Cache-Control Header

5. Gzip Components

6. Put StyleSheets at the Top

7. Put Scripts at the Bottom

8. Avoid CSS Expressions

9. Make JavaScript and CSS External

10. Reduce DNS Lookups

11. Minify JavaScript and CSS

12. Avoid Redirects

13. Remove Duplicate Scripts

14. Configure ETags

15. Make AJAX Cacheable

16. Use GET for AJAX Requests

17. Reduce the Number of DOM Elements

18. No 404s

19. Reduce Cookie Size

20. Use Cookie-Free Domains for Components

21. Avoid Filters

22. Do Not Scale Images in HTML

23. Make favicon.ico Small and Cacheable