I first saw Yahoo's 13 Simple Rules for Speeding Up Your Web Site referenced in a post on Rich Skrenta's blog in May. It looks like there were originally 14 rules; one must have fallen off the list somewhere along the way.
1. Make Fewer HTTP Requests
2. Use a Content Delivery Network
3. Add an Expires Header
4. Gzip Components
5. Put CSS at the Top
6. Move Scripts to the Bottom
7. Avoid CSS Expressions
8. Make JavaScript and CSS External
9. Reduce DNS Lookups
10. Minify JavaScript
11. Avoid Redirects
12. Remove Duplicate Scripts
13. Configure ETags
It's solid advice culled from the excellent Yahoo User Interface blog, which will soon be packaged into a similarly excellent book. It's also available as a powerpoint presentation delivered at the Web 2.0 conference.
I've also covered similar ground in my post, Reducing Your Website's Bandwidth Usage.
But before you run off and implement all of Yahoo's solid advice, consider the audience. These are rules from Yahoo, which according to Alexa is one of the top three web properties in the world. And Rich's company, Topix, is no slouch either-- they're in the top 2,000. It's only natural that Rich would be keenly interested in Yahoo's advice on how to scale a website to millions of unique users per day.