Exactly as Luki said. I sometimes leave the browser open at this forum to increase my Total Time Logged In, just for laughs (yes I'm a cheater), but there's the following bug:
If you keep it open for more than an hour, when you refresh, the hour+something you have just spent on the forum are completely gone. You need to refresh often, and log out and in again after an hour (actually I'm not sure if it's exactly an hour, might be more).