Forums/Threads as read?

This thing is wierd:
-When i read a thread i'm expected to see it read afte i read any page of it. But i this forum it's always unread
-After a certain amount of time spend on this forum all the forums/threads appear read but i only read on thread in that period of time. It becomes annoying: I wan't to explore the forum, maybe help someone but when i take a break or something all the forums appear read and I don't know which messages I read or not. But this part with forums happend only at my school(where we have some strict measures) but i don't get the same problem from other forums at school.

It should be marked as read as soon as you read it - it is for me. Do you have cookies disabled in your browser?

Cookies are working(generally) but i can't manage them on the school computers.

5 minutes ago all the forums have been marked read but all i read is my own posted thread.