Firefox: Add a Trusted CA

The default Firefox comes with certificates from well-known commercial CAs. My ISP is also CA and Firefox cannot verified it because the CA is not recognized. How do I force Firefox to accept my ISPs certificate?

Like many apps Firefox needs to have a certificate from the CA that signed the web server’s certificate. However, you can import a new CA certificate into Firefox version 3.5 using the following simple procedure:
Fire a Firefox browser (i.e. Launch Firefox)
Choose Preferences from the Edit menu.
Click the Advanced button.
Select the Encryption pane.

Fig.01: Firefox View Certificate

Click the View Certificates button.
Click the Authorities tab.
Click the Import button at the bottom of the screen.

Fig.02: Firefox Install / Import CA Certificate

Navigate to the CA certificate and import it.