I was able previously to access my webmail email server (https://webmail.centurylink.net/) but Firefox is now completely blocking my access. The details I get back from Firefox is:

Secure Connection Failed

The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.

What can you do about it?

The issue is most likely with the website, and there is nothing you can do to resolve it. You can notify the website’s administrator about the problem.

Error Code: PR_CONNECT_RESET_ERROR

Why? If I want to go to a site that is MY business not Firefox's