Rules for High Performance Web Sites
These rules are the key to speeding up your web pages. They’ve been tested on some of the most popular sites on the Internet and have successfully reduced the response times of those pages by 25-50%.
The key insight behind these best practices is the realization that only 10-20% of the total end-user response time is spent getting the HTML document. You need to focus on the other 80-90% if you want to make your pages noticeably faster. These rules are the best practices for optimizing the way servers and browsers handle that 80-90% of the user experience.