The website is all contained on a wiki.
You can also click the edit button when viewing the website which is located on the bottom right of each page.
There are a few special pages; for example the Navigation page is the left hand navigation bar and the QuickLinks is the top right navigation bar.
Note that after you've changed the wiki it can take a few minutes for the HTML website to be updated. If you append ?refresh=1 to the URL then the website is usually updated immediately.