The Exceptional Performance team has identified a number of best practices for making web pages fast. The list includes 34 best practices divided into 7 categories.
Minify is a PHP5 app that can combine multiple CSS or Javascript files, compress their contents (i.e. removal of unnecessary whitespace/comments), and serve the results with HTTP encoding (gzip/deflate) and headers that allow optimal client-side caching. This helps you follow several of Yahoo!'s Rules for High Performance Web Sites. (See "Problem Domain" below for more info.)