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

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

http://kb.mozillazine.org/Error_loading_websites

• uses an invalid security certificate SSL_ERROR_BAD_CERT_DOMAIN
• configured their website improperly

How to troubleshoot the error code "SEC_ERROR_UNKNOWN_ISSUER" on secure websites

https://support.mozilla.org/en-US/kb/troubleshoot-SEC_ERROR_UNKNOWN_ISSUER

Chilkoot said

I can get to the main site, http://www.virtualwall.org/ but clicking on 'any' of the links & Firefox says it is configured incorrectly.

• • • uses an invalid security certificate. The certificate is only valid for the following names: *.readyhosting.com, readyhosting.com Error code: SSL_ERROR_BAD_CERT_DOMAIN

This site is not meant to be used with an HTTPS address. Every address on that home page you linked to is a plain HTTP address. Are you using any extensions or external security software that force HTTPS on sites? If so, see whether you can work around that, if necessary, you can edit the address in the address bar to change https:// to http://.

Mozilla's 'security' doesn't allow me to visit many sites including my own and there is no override. It must be wonderful playing 'god'.

Sometimes the problem is not the browser, but other programs.

Hi Chilkoot, this is a problem with the protocol on your requests to the site. I would expect you to receive the same rror if you try to view https://www.virtualwall.org/ in other browsers on your system.