I am not able to phrase myself how to xplain this problem so i wil just post my situation , you shal understadn what it is.

I enter a forum , suppose only 2 topics have unread post. I read them and close the forum. Next time i enter the forum , only one unread post is there that to in a new topic. read it and close .

Now the next time i enter the forum those old topics again say unread whereas no newer posts are there than those i checked the first time.

I close the browser after every check . This is happening over days. Why is this happening?

Might be that you have old cookies. Clear your cache first then try.