You can mark all topics of a forum as read in Web Forum Reader without looking through them all. To do so:

1. Select the resource in which you want to mark all topics as read.
2. Select the Mark All Topics as Read item in the Commands menu or press the Ctrl+R shortcut.

If you mark all topics of the resource as read, whereupon made the synchronization, you'll see all new and changed topics that appeared on the resource after the time of the previous synchronization.