We do have a giggle when we see a page with this error message.

Your connection is not secure

In this instance we were using Firefox to access Google Adsense: https://www.google.com/adsense/

We visit this page most days, so we “know” the link address is OK.

It’s very kind of Firefox to alert us so the question is: is it Google’s problem or Firefox?

We can answer that: it’s Firefox

We open Google Chrome, login to the same address without an issue or warning.

It is one of the reasons we stopped using Firefox.

Too many errors when the error appears to be Firefox.

ERROR MESSAGE

Your connection is not secure

The owner of www.google.com has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website.

This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox only connect to it securely. As a result, it is not possible to add an exception for this certificate.