This means that Firefox reached the end of the list with the builtin cipher suites and wasn't able to find a cipher suite that the web server supports. This can happen because you have software that intercepts the secure connection and that acts as a man-in-the-middle. You can check whether your security software is covered in this article. *https://support.mozilla.org/en-US/kb/error-codes-secure-websites You can check the server. *https://www.ssllabs.com/ssltest/ You can check your browser to see if there is a matching cipher suite. *https://www.ssllabs.com/ssltest/viewMyClient.html