What does mark all fourm read do?

What does mark all fourm read mean? If it mean to clear all of the red stars than its not working... :o

That's what it is supposed to do although I have never tried it. I'll see if I can fix it :D

I'm thinking: You see whenever you log in there are new topics with a piece of paper in front of the topic right? If you use mark all then even the old topics will all be marked as read.