[stomachmonkey]

He's on a Mac. Not malware.

Which browser are you using? Safari, Firefox or Chrome? Just enable pop up/ad blocking in the browser preferences.

You don't need to restart either, you can kill a program by holding Command+option keys then hit esc. Brings up the force quit dialog. Select the app and hit force quit.

If you are into command line you can also run Terminal and do a standard kill pid.

Oh, and run software update to make sure you have latest security patches installed.