This site is designed to take advantage of CSS. If you are seeing this, CSS must not be available or enabled in your browser. Everything should still work, but won't be as pretty. :)
Firstly, you need to have set up a valid mail configuration in Apple Mail (or possibly other mailers). You also need to make sure that the From address you specify uses the same server as one of your Mail configuration, as it finds the configuration based on the server domain.