There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connection certificates and send their own.

https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can

https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites

https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message

https://support.mozilla.org/en-US/kb/connection-untrusted-error-message

Websites don't load - troubleshoot and fix error messages

http://kb.mozillazine.org/Error_loading_websites

What do the security warning codes mean

This certificate is valid only for weebly.com, not for www.bambergertrivia.com.

Hi Dave, do have the HTTPS Only setting turned on? That's one reason Firefox might have started trying to access your site using an https:// address instead of an http:// address. More info on this feature, how to turn it on/off, and how to make exceptions: HTTPS-Only Mode in Firefox.

By the way, if you do want to enable secure access to your site, Weebly has an instruction page, but I'm not sure about the step where you need to update your DNS. Probably best to check with all the companies involved to make sure it goes smoothly.

https://www.weebly.com/app/help/us/en/topics/enabling-ssl-for-your-site

This website only works when accessed via http:// and not via secure https://.

Firefox should show a warning and allow to go to the HTTP version.

You can disable HTTPS-Only mode by clicking the padlock icon in the location bar and disable HTTPS-Only for this origin (protocol and hostname).

• https://support.mozilla.org/en-US/kb/https-only-prefs