1.) Use CTRL + F4 to close the offending browser tab (Press the CTRL key and the F4 key on the top row of your keyboard).
And...if that does not work...
2.) Press ALT + F4 to close all open browser tabs.
And...if that does not work...
3.) Open Task Manager by pressing the CTRL+SHIFT+ESC keys. In Task Manager, click on the “Processes” tab at the top. In the list of processes, right-click on each instance of your browser you see running and choose “end task”. Note: Google Chrome usually shows a process for every tab open and every Chrome extension running. You’ll need close as many of these as necessary until you see the browser window with the scam in it close. Browser processes for the most popular browsers show as chrome.exe, firefox.exe, iexplore.exe (for Internet Explorer) and Microsoft Edge.
And
if you still can't get the scam advertisement(s) closed:
4.) Press
and hold down the Windows key and tap the R key. Type SHUTDOWN /R
in the Run box and press Enter. This will restart your computer and close
all open programs.
Make sure when you restart your browser or your computer, when your browser asks if you want to restore the tabs that were open, you want to decline - otherwise, there's a good chance you'll find yourself right back where you started with the scam popup.
If you're prepared, you won't panic. When you panic it's hard to think straight.
BE PREPARED - NOT SCARED.