While reading a link posted in FB, had annoying ad with "x" in the corner that indicated it could be closed I thought, but instead started opening up another page and then a pop up ("you've won a prize!") with no way of closing it except clicking on the "OK" button. Tried closing and restarting Safari, logging out and logging back in, and restarting entire computer - still comes up. Cannot get to Safari preferences. Any ideas for me?