It seems that the top area of the trackpad is a 'swipe area' which enables back (right to left) and forward (left to right) funtionality when using a browser. (I guess the trackpad is too small to get the proper macbook 3 finger swipe to work!) I couldn't work out what was happening at first, but now I know it's there, I actually find it useful and quite like it. I think the problem is the pad is so small it's easy to accidentally 'swipe' back or forward when you just want to move the cursor. But chill out and move the cursor a little slower and it's not a problem.