Firefox 37 raised the bar a bit on SSL connections, so problems have been reported here with some sites since it was released a few weeks ago.

Do you want to post the address of the page generating the error?

If you have noticed a pattern of problem sites or added any exceptions, then it may be an issue with settings or with other software on your system. We'll have more questions in that case to try to get to the bottom of it.

MaccT said

Just today I cannot access a web site I frequently access. The error I get says - the website uses an invalid security certificate - The certificate is not trusted because no issuer chain was provided. (Error Code: sec_error_unknown_Issuer). How can this be resolved? I am using Firefox Version 37.0.2, and widows 7

This problem first occurred last evening, I will see if the Site Web master can offer a fix first.

The website may try to fallback to TLS 1.0 in a way that is no longer allowed in current releases or may be using a deprecated cipher suite.

You can open the about:config page via the location/address bar and use its search bar to locate this pref:

• security.tls.insecure_fallback_hosts

You can double-click the line to modify the pref and add the full domain to the value of this pref. If there are already websites (domains) in this list then add a comma and the new domain (no spaces). There should only be domains separated by a comma in the Value column (example.com,www.example.com).

If this helps then you can contact this website and ask them to look into this and update their security.

• https://developer.mozilla.org/en-US/Firefox/Releases/36/Site_Compatibility#Security
• https://developer.mozilla.org/en-US/Firefox/Releases/37/Site_Compatibility#Security