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/







Enabling CSS merging breaks the checkout in Magento.
Why? Because they compile the css with absolute paths, making a secure checkout page reference unsecure files (those same css files).
Not recommended for any store that uses SSL for checkout.
Wow, that would be one beast of a download. I’m very new to Magento but am finding it to be quite a bit slower on shared hosting than I had anticipated: I was hoping this post would be about improving performance.
Previous commenter left a really good point about the secure checkout page potentially breaking if using secure checkout page.
We discuss the https bug and a solution for CSS merging here: http://magebase.com/magento-articles/magebase-news/magento-1-4-feature-to-merge-css-files-and-https/
@Brian – I’d never run a magento site on shared hosting unless the hosting plan is specifically optimized for magento.
Magento is like a Ferrari you won in a competition. It comes for free but to run it, you got to have the appropriate resources.
Good tools, but yslow best for me.
Yes. magento if it not enterprise not so fast as you want
We recommend some similar things over at TinyBrick. It’s great to finally see someone break down the anatomy of a web-page request. We have a slightly less-technical take on it over at: http://guides.tinybrick.com/magento/speed-testing
It’s truly amazing though, the number of requests and the inefficiency that people build into their sites and have no clue about.