I mean the little corner-turned-down page icon. When I mouse over that, the little box that pops up says "Unread Posts."
It
used to be the case, in the last version of the forum software, that button would take me directly to the first unread post - it would load the page already scrolled halfway down or whatever, to the first unread post's location. This is a pretty common feature on forum software.
Now, it just takes me to the top of the page that contains the first unread post. I then have to either scroll down to the first unread post, or click this link:
Honestly, none of this is a big deal. One extra click isn't gonna kill anyone. I just thought it was worth bringing up as a feature that did work on the previous forum but got broken (or intermittently broken) in the upgrade.