What site is that is causing that?

Although I've gotten the screen several times there is no reproducible site. One Google search that did raise the screen had the URL https://www.google.com/search?client=firefox-b-1-d&q=symfony+swiftmailer.

If such a screen is not a function of the browser, what other source might there be? I have done a security scan on my system and not found any aliens.

Do you use any ad blockers or Firefox's Tracking Protection feature? Sometimes there is an overlay in front of a page with an ad which gets stripped off, but you still need to close the overlay in order to access the content. (At least you have a button; if the button gets stripped out, too, you get stuck.) You could test with your "blockers" disabled and see what happens.

Interesting suggestion. AdBlocker is installed. I've not yet been able to reproduce the problem after restarting Firefox. We'll see...

Attached is a screen grab of the CONTINUE screen.

Hi truckeesolutions, does that appear when you are first loading the results page, or when you click a link to leave the results page? Either way, I don't expect to see that on Google's site.

One possible culprit would be an extension. You can view, disable, and often remove unwanted or unknown extensions on the Add-ons page. Either:

• Ctrl+Shift+a (Mac: Command+Shift+a)
• "3-bar" menu button (or Tools menu) > Add-ons
• type or paste about:addons in the address bar and press Enter/Return

In the left column of the Add-ons page, click Extensions.

Then cast a critical eye over the list on the right side. Any extensions Firefox installs for built-in features are hidden from this page, so everything listed here is your choice (and your responsibility) to manage. Anything suspicious or that you just do not remember installing or why? If in doubt, disable (or remove).

Any improvement?

@jscher2000: After removing the redundant add-on AdBlock the CONTINUE screen has not reappeared. Thanks for the lead.