Pop-up window doesn't close
Safari shows a pop-up saying "http://exclusiverewards.rewardingzonez.com" and "Congratulations, You are today's lucky visitor, Press OK to continue" I can't close the window and can't go to any other window either. Forced closing of Safari doesn't help as the pop-up is there again when I re-open Safari. Closing the computer doesn't help either nor pressing OK in pop-up. Any ideas how to force the window to close (can't select "close window" from the toolbar)?
MacBook