What are the light bulbs that sometimes appear beside the forums on the main page? At first I thought they might indicate unread posts, but that doesn't seem to be it.

Actually, I think it does indicate new posts. It seemed to not do that earlier, because I went directy back to main page instead of going back into the particular forum first.

It means that new posts have been posted that haven't been viewed yet.

Yeah, I thought that was what it was supposed to mean, but it does not work too
hot or something. For instance, I checked a couple of forums I seldom read and there
were new posts, today, but there were no light bulbs announcing the posts. Does it
possibly only work in forums one has prior posts in?

I guess... I think the program assumes you care enough about a topic if you post.

Well I take that back.. I see a lightbulb near almost every forum... some I never read.