Website Performance

Or "How to make my website faster?"
Steve Souders says that he is the YSlow creator, which is a Firefox's and Firebug's extension that calcs the conformity degree of a site with th rules for high performance websites. Now he says he got "14" new rules but lists only 10. Now I will list the current 34 YDN rules plus the 10 "new" ones:

1. Make Fewer 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. Flush the Buffer Early
16. Use GET for AJAX Requests
17. Post-load Components
18. Preload Components
19. Reduce the Number of DOM Elements
20. Split Components Across Domains
21. Minimize the Number of iframes
22. No 404s
23. Reduce Cookie Size
24. Use Cookie-free Domains for Components
25. Minimize DOM Access
26. Develop Smart Event Handlers
27. Choose <link> over @import
28. Avoid Filters
29. Optimize Images
30. Optimize CSS Sprites
31. Don't Scale Images in HTML
32. Make favicon.ico Small and Cacheable
33. Keep Components under 25K
34. Pack Components into a Multipart Document

1. Split the initial payload
2. Load scripts without blocking
3. Don’t scatter scripts
4. Split dominant content domains
5. Make static content cookie-free, repeated
6. Reduce cookie weight, repeated
   
7. Minify CSS, repeated
   
8. Optimize images, repeated
9. Use iframes sparingly, repeated
10. To www or not to www

I would like to add 2 rules that I readed elsewhere:

1. Optimize inner loops
   
2. Make XHTML web pages
   

The first one is explainable from the programmer's point of view: the inner loops are the greatest time consumers, and by optimizing them you gain computational time. For articles dealing with how to do that with JS read this and this too.

The second rule applies to mobile web development, where hardware resources are fewer, and complete browsers slowers than browsers that read only XHTML. Visit http://validator.w3.org/ to validate your website.