I suspect you’ve gotten an ad with a script that will not let go. . . Adware on the ad. Quit Safari, delete the history, and it will go away when you restart Safari.
Good suggestion. Trying, will be back shortly with update....
Alas, no change. Wiped my history for all time (had to login to FR from scratch just now), but as soon as I hit the Dilbert blog page, a small overlay appeared in the upper right (”Open” “Get App”) and after 10 seconds the blog page redirected to a scary bogus page and a pop up dialog to download the “Free App”. Same as before.
Bollocks. I guess I’ll check again in the morning. Presumably somebody will write to Adams. Maybe I will if it’s not better tomorrow. And I’ll check some other platforms.