What does the exclamation mark next to 'Forum' mean?
The exclamation mark means there are new messages in the forum.
When you visit the forum, another exclamation mark will indicate on which board new messages are posted. And when you go to a board, the exclamation mark indicates at which topics new posts are present.
Once you've read the posts, the exclamation mark will be removed. So it's easy for you to track which posts you've read.
If you're not interested in reading the new posts, click on 'Forum' in the menu. There you'll find a link that says 'Clear all exclamation marks'. Clicking on this will mark all posts read, so the exclamation mark disappears and will only reappear when new forummessages are posted.