There is also a number next to this link, that indicates how many ppl (if any) are currently inthe chat room. Using this and the listing of ppl who have visited the forums in the past 15 mins, sometimes the timing can coincide and a chat ensues..
For example i see Alan has recently visited the forums.. Now if I click the chat thing and wait in the chat room.. hopefully he is still online and sees my name in the recent visitors list, and also that there is 1 person in the chat room. Then if he joins the chat room voila!
