A rating system is a great tool for any website. It serves two important purposes: first, it gives your users a way to interact with your pages-and interactivity is an important aspect of any website these days. Second, it provides you with a valuable feedback tool that you can use to gauge viewer interest in individual areas of your site. In other words... everybody wins!
He explains the concept behind the system before ever getting into any code - a visual representation of the rating users are giving a particular article/posting. With that out of the way, he gets into the HTML first, explaining how the table is laid out before giving the code to pull together the images and form one seamless one representing the correct rating. He also demonstrates the use of a "secret hash" to protect the script against abuse.
Of course, the code is available for download as well.