They have a nifty add-on called the web developer. It allows you to view and edit the CSS for any webpage. As you edit the code, the changes go live on the page you are viewing. None of the info is actually changing anything on the real webpage though.
Once you get the code correct, and the page looking like you want, it is easy to just copy and paste the code to your webhost and the page will go live with the corrections. It is pretty neat how it all works.