YSlow for analyzing your web site

In the Problem with WebSphere Portal performance entry i talked about how browser is spending most of the time in getting HTML from portal but major portion of time is spent in downloading and executing other resources.

So i started thinking about what i can do to make the portal site browser friendly (So that my pages render fast). It seems that Google and Yahoo has done lot of research on how to improve web site performance.

Yahoo has created a YSlow tool that we can use to analyze the performance of web page, they have following set of rules that they apply to web page to figure out if its browser friendly and based of the rules it gives us suggestion on what can be done to improve performance of the page

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

When i did YSlow analysis of the portal page with default IBM theme and no portlets i got quite a few suggestions on what i can do to improve performance. I am planning to make these changes and see how it helps.