When viewing a page, how do you stop it from automatically droping to the bottom of the page?

Sometimes when viewing a page it skips to the bottom of the page. I try to use the slide on the right to control it but it ignors my mouse and drops to the page bottom. I try to restart the system and it does not help. Once it starts this dropping phase. I have to close the laptop and go about another task. This is most ignoring.