What's going on here

[cqdx73]

I was just reading an article on the " Howstuffworks " site, clicking my mouse one , two, or three clicks at a time. My pointer was resting on down arrow of the scroll bar. Since I have a track ball mouse I made sure that I left my finger off of the ball and only touched the mouse with my thumb and all I was doing was operating the clicker button. Scrolling the page slowly as I read the info before me. Suddenly it scrolled all the way to the bottom of the page, seeming to have a mind of its own.

Can anyone explain this for me or suggest some possible causes or fixes.

So thanks in advance.