Options/Preferences > Advanced > Certificates > "Add Exception" is where you can add a local cert. There was also a new ca cert [https://blog.mozilla.org/security/2014/04/24/exciting-updates-to-certificate-verification-in-gecko/] If there are any issues please file a bug. [Self-signed certificates make your data safe from eavesdroppers, but say nothing about who the recipient of the data is. This is common for intranet websites that aren't available publicly. ] via [https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message]. This may be helpful as well: [https://support.mozilla.org/en-US/questions/1002237]