Do you have a windows computer? If so, and if you're using firefox-then you go to tools, "my add ons," and delete it from the add ons, or extensions.
If you can't get rid of it there-then you have to hit "start," and go to your control panel, from there find "add or remove programs," wait for the list to populate. . . .and it would have to be there.
Another thing you can do is delete your browser with all of it's settings, and re-download the browser without any of the previous settings. You have to look for the little boxes to see those options when un-installing and installing.
If you're using internet explorer-then STOP USING THAT CRAP! Internet explorer is the worst browser in the world, and you can download firefox for free, or Safari, or Opera, or Google Chrome. . . .any of those for free.