This screen shot was made today, April  13.

As you can see, it was while trying g to get on Google.


This has been happening very often. No explanation.

I have talked to the ISP and got no explanation. My connection will often work for hours without this error.

Any ideas?
There is a Mozilla Support article on this.

Buggy add-on?
Do you remember installing any add-ons around the time this FIRST HAPPENED?

I would probably start with the 'Troubleshoot extensions, themes and hardware acceleration issues to solve common Firefox problems'

Or for advanced users there is the option to disable that error message.Thanks for the reply.
It will take me time to read  the Mozilla articles.

Yes,  I do have add-ons. I will disable  them and see if that helps.
BTW. I have had a similar message on CHROME.
Also, the message happens when I get a DSL error on my modem. But how can I know if ones is the cause of the other?
I have Alvira free version, full scan shows nothing. Today Malwarebytes showed nothing.

If Firefox the newest stable version?

The only time this ever happens to me is on websites with INVALID security CERTIFICATES but I don't think it has ever happened on a Google website.