When developing a web site, it's a good idea to keep usability in mind. One can make usability studies in order to find out how to improve the design of his web site, but good usability studies can be expensive. Another good alternative I often resort to is to follow the findings of large companies that have already invested in usability studies. Their findings can be safely assumed to be strong indicators to what a site with good usability should be like.
Have a look at how Google redesigned its Google Base homepage. Google is a big fan of usability.