How does it work?

I have been visiting these forums from a long time but I couldn't figure this out.
When I view the topics for a forum, there is either a yellow folder image or a red folder image on the left sife of the subject. In the legend it says that, red folder means 'new posts since my last visit and yelloe means no new posts.
But even after I read the posts, I still see the red folders as red. In fact, even when I logon later, it still shows me the folders I already read in red color!!!
How doe this work?? It irritates me too much. I mean, I click on it hoping that it has a new message but it is not so!!
thanks,
Dinesh.

de problem is ...its some ting to do with u r browser cache.. since de session iz de same de pages get half loaded from cache.. esp . in IE..
Regds
Gautham Kasinath
U R not Alone..

It never seems to be all that accurate to me. It's trying to do smart stuff with javascript, but javascript is riddled with limits.

Actually it's based on your last visit to the forum. So if you visit at 10am then again at 11am, at 11am all posts made since 10am will be marked as new. They will stay that way as long as you continue your 11am visit. If you go away and then come back at 1pm, then all posts since 11am will be marked as new. Whether posts are marked as new or not has nothing to do with whether you actually looked at the posts.

Thomas, that seems to be it. But how does it know (or figures out) that I 'went away'??? I mean, what actions makes it infer that i went away and I came back?

Whenever you re-load the main topic page,that seems to count as "coming back". It doesn't matter if you were really gone all the time since your last re-load, or if you were staring at your screen the whole time. So somewhere it's just remembering the time of the last load/re-load.

...and so if you're seeing old messages marked as new, you need to hit the refresh button on your browser. Even if you did physically go away, or even disconnected from the internet, your browser may have cached the page for you. Refresh will force it to get a new copy.

It's saving the information in a cookie. But reload doesn't do anything for me. It's when you go to this address:
http://www.javaranch.com/cgi-bin/ubb/Ultimate.cgi
If you notice, the internal links within UBB all have BypassCookie=true appended to the main page links. This prevents the cookie from being rewritten with a new date and time.