I made a small research regarding  Magento performance. Perhaps, you already know it, but I would like to share this with other people who probably haven’t heard about this problem.

Do you know how many HTTP requests does standard Magento  with default template make?  I have tested Magento and I’ve got very interesting info, 111 HTTP requests! I think it’s too much especially if you add a lot of new pictures, which you will use in your adjusted template. Then  the number of http requests can increase to 150! Every element requires an extra http request. Perhaps, not when the cache is full, but definitely when the cache is empty.

I used a free tool called  “Web Page Analyzer” .

I’ve got the following results: the total number of requests on this page is 111 which by their sheer number will be one of the  main causes of the web page delay.

My suggestion is to try to decrease the number of http requests to some reasonable number (about 20 – max 40) and your web page will have better performance.
First step: try to clear css file and remove some unnecessary images or try to use CSS sprites.
Second step: go to Magento admin and click: System -> Configuration -> Developer and enable next options: “Merge JavaScript Files (beta)” and “Merge CSS Files (beta)”.

Also, you can find more useful data with this free tool like: Total HTTP Requests, Total Size of page, page objects together with getting the diagnosis and some recommendations.

I hope it will help you optimize your web page.

Some interesting links:
http://www.yuiblog.com/blog/2007/04/11/performance-research-part-4/
http://www.websiteoptimization.com/speed/tweak/parallel/

Source: http://inchoo.net/ecommerce/magento/magento-performance-research-and-improvement/