You can check who is the issuer of the certificate(s).

You can retrieve the certificate and check details like who issued certificates and expiration dates of certificates.

• Click the link at the bottom of the error page to expand this section: "I Understand the Risks"
• Click "Add Exception" and let Firefox retrieve the certificate ("Get Certificate")
• Click the "View" button and inspect the certificate and check who is the issuer.

You can see more details like the intermediate certificates that are used in the Details tab.

If that isn't possible then try this:

Open this chrome URI by pasting or typing this URI in the location/address bar to open the "Add Security Exception" window and check the certificate:

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

In the location field type/paste the URL of the website

• retrieve the certificate via the "Get certificate" button
• inspect the certificate via the "View..." button

chubbles said

I was getting messages that update failed, I think this was caused by Lastpass update. I tried a refresh and my problem started. Tried uninstall lastpass and FireFox then download Firefox(37.0.2), still have the problem. I can set Protopage as my home page, but any bookmarks that lead to a https site get the untrusted connection. I tried several different search engines, same result. I'm running a mid 2011 mac mini. Please help I've been using FireFox for many years and many computers and I love it. THANKS!

ouch I hit the wrong button!!!!! cor-el I give you 10 "adaboys"! You showed me my problem, it was Avast, which I thought I had uninstalled, obviously not properly. Avast was the issuer in every case. High 5 for cor-el!