Sean Corfield has posted some information on the navigation at Macromedia.com and how it uses Local Shared Objects to remember where you last visited.
You can view Sean’s post here.
There is also an article on the DevNet center which discusses some of the design elements of the site, including the navigation. You can view that article here.
Of course, if you don’t want / need to use the advanced / customized navigation, you don’t have to. Just use the navigation bar at the top of the page to find the information that you need (although you will probably have to go through more page refreshes).