The active members page is the page the shows who is on line and what they are doing. Go to the bottom of the forum and look for the "What's going on" Section. The section immediately following that is for "Currently Active Users." Click on the "Currently Active Users" words and it links you to a page showing who is doing what. This is the page that auto refreshes (or at least that is my understanding) that will keep you signed in.

http://www.bdsmlibrary.com/forums/online.php

I also use the chat screen to keep me logged in as well. Although I seldom have the problem even when I don't have an active page open. *shrugs* Sorry, not sure I have any other suggestions!