Hello Kaily, yes the server apparently cannot be found when I tried it a minute ago.
However, while you are waiting for that to sort itself out, there are some very good threads explaining AVRT in depth on here. Algorithm knows AVRT inside out and all of his posts are informative.
If you read any of the threads posted by newcomers to AVRT, members here have given a wealth of information to them.
Tatsys thread when she was starting out here, Flame11 and BeHappy have tons of information from people who explain the ins and outs of AVRT
If you search the AVRT threads on here, I think you will find a lot more information than is on the basic crash course on the RR website.