Sorry to hear you that you unable to access this site. Here, I have the following solution of "Issuer certificate is unknown". This type of error usually arises when the file cert8.db in your profile folder has become corrupted. In order to fix the problem, we will have to delete the file while Firefox is closed. To do so, we will need to find and open the profile folder. This can be done by clicking the menu button New Fx Menu , clicking help Help-29 and finally selecting “Troubleshooting Information”. Once the troubleshooting information page opens, select the “Show Folder”. When you have successfully opened the profile folder, close firefox and delete the cert8.db file.

Occasionally, certain browsers will give this error when others do not. For example, Microsoft Internet Explorer can automatically download intermediate certificates the first time you visit a site that needs one while Firefox cannot. Once a trusted certificate is installed properly, all browsers will work without getting this error. You can verify whether the certificate will get a certificate not trusted error by using our SSL Checker. The SSL checker uses the latest roots included in Mozilla's Firefox to determine if a certificate is trusted. For specific compatibility of your certificate see, SSL certificate compatibility. Visit: www.sslshopper.com

I had already tried deleting the Cert8 file as previously noted.

Second paragraph sounds like promoting third party website, I would prefer to try to get Firefox fixed for this user account.

Thanks

You would need an older copy of the cert8.db file if it was working previously.

You can check if you have an "Old Firefox Data" folder on the desktop if you have used the Refresh feature in Firefox.

If you can't inspect the certificate via Advanced (I Understand the Risks) then try this:

Open the "Add Security Exception" window by pasting this chrome URL in the Firefox location/address bar and check the certificate:

• chrome://pippki/content/exceptionDialog.xul

In the location field of this window type or paste the URL of the website with the https:// protocol prefix (https://xxx.xxx).

• retrieve the certificate via the "Get certificate" button
• click the "View..." button to inspect the certificate in the Certificate Viewer

You can inspect details like the issuer and the certificate chain in the Details tab of the Certificate Viewer. Check who is the issuer of the certificate. If necessary then please attach a screenshot that shows the Certificate Viewer.

cor-el,

Thanks for your reply. I actually could not confirm that your suggestion would work as my computer died, so I no longer have that issue! This also explains my delay to responding to your post. Thanks again for your suggestion.