This is the way it makes sense for me Wiwi. The main page indicators do not indicate whether or not you have read the post, but merely show that a new post has been placed in this section since your last visit. Once you drill down inside that section, those indicators show new posts that have not been read and will turn from yellow to grayish blue after you have read the message. I didn't care for this too much at the start, but once I came upon this miraculous discovery it made things a lot less complicated. Once you have caught up on your forum reading, go down to the bottom like Pointman said and click "Mark all forums as read." This will clear the main page indicators so that when you return only those sections with new posts will show up. You can also logout to reset the forum when you are done and log back in when you return.
Hope this helps man.
"It's the Administrators that make a forum, not the indicators!"
-COG Brother 10/28/02