how-to block ads
Each forum USED to have a "clear" option at the top, since removed. To clear an individual forum, just click on either the first red or yellow envelope on your Favorites page. That will mark all messages read and will clear them off your Favorites page until a new post is made in a thread. (Thanks to Sashwa for posting this info.)
There is also a feature to clear all of the forums in your favorites, as seen here:
NOTE: If you don't see the "clear all" links, try changing the Slow / Quick links above the forum list on the left.