As far as I understand, you can talk about pretty much everything as long as you don't forget to apply common sense (i.e. no spam, no pornography, no advertising (talking about other pages is ok, but don't post things like "Go to this page111"), no clicking buttons more than once, no loafing, no using smileys, no funny hats, no loud breathing, no running, no walking, no standing, no complaining about anything, no whistling, no dancing, ... I think I got carried away...)
Anyway, just the first three things I mentioned.
EDIT:
*looks up*
Oh, uh.... never mind.