Firefox refusing access to some sites, which are available on internet explorer

You can click the "Advanced" button to expand this section and show extra details. You can click the blue error message to expand this section. If the certificate is not trusted (SEC_ERROR_UNKNOWN_ISSUER) then click "Copy text to clipboard" and paste the base64 encoded certificate chain text in a reply. That will allow us to check details like the issuer of the certificate. See also: *https://support.mozilla.org/en-US/kb/what-does-your-connection-is-not-secure-mean *https://support.mozilla.org/en-US/kb/troubleshoot-time-errors-secure-websites *https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message