1. I'm going to assume that you have no idea what a userbar is (Prove me wrong then)? ...
Not exactly no idea at all; however, I have never downloaded one. I rarely download a program.
I associate the word "user bar" with the generic term "tool bar" with which IE come equipped -- and which various sofeware peddlars will gift you with. For example, Google offers a free one. Some
of these carry along all kinds of spy-ware including the kind that reports back your key strokes and comprises your privacy (if you have any left).
Now if it's something completely different, I certainly would appreciate a description.
Well, I found this description on Wilipedia, a small rectangular picture with which users use to in their signatures in the internet forums, which indicates about their personality or hobbies
I would call that an avatar. If it's animated, it probably uses Java Script -- which can harbor hidden stuff.