Increase Website Performance

As I have I am interested in website design again I was looking at ways to increase website performance. The best information I found was best practices for speeding up website at yahoo

The main factors of increase website performance are

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. Post-load Components
17. tag: content
18. Preload Components
19. Reduce the Number of DOM Elements
20. Split Components Across Domains
21. No 404s
22. tag: content
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

The amazing thing for me is I thought I could be considered a website developer but I don't understand half the factors I have listed above in improving website performance.