I am working right now on a forum and I'm almost done, but now I came to a point where it kinda got difficult.
You're probably familiar with the phpBB forum. There's this cool feature which flags posts as read and unread.
I found here a similar thread about this, but I didn't really get the solution.
If I save the time when the user logs in and mark all posts which have been created in the past, it might work. But now, what's next? The user read an unread post and I want to mark it as "read" but the other posts should still stay flagged as "unread" until he reads them. I kinda have to store this data, don't I?
And I've actually been also thinking about saving that data in cookies. How about that?