Nice work, it looks great and its full of useful information that could really help newbies to Newgrounds
Few bugs I will mention though, on the ranks page the rank descriptions are hidden behind the buttons lower down so you need to make sure the buttons at the top of the pages are on a higher level than those below.
I'll also echo what's already been said about the Back, Continue, Menu buttons - you need to make the active area bigger than just the text.
Nice idea for the right-mouse menu, but all the options lead to the Newgrounds Alpha's page.
Wasn't sure what the recommended programs had to do with Newgrounds really, but I guess they could be useful for some people. Linking to the trial of the latest flash in that section might have been a good idea (even though you put it on the right mouse menu as well). I wouldn't personally have put Limewire on there, and encouraging illegal music downloading, but hey. Maybe use the home websites of the programs, which are more likely to have the latest version rather than download.com?
The credits surprise? No. Don't go there. Just don't.