How to fix Your connection is not secure|Error code: SEC_ERROR_UNKNOWN_ISSUER

How to fix Your connection is not secure|Error code: SEC_ERROR_UNKNOWN_ISSUER-your connection is not secure-your connection is not secure firefox sec_error_unknown_issuer. I get the following error message while try to access the mozilla firefox: Your connection is not secure The owner of www.indiapost.gov.in has configured their website improperly. To protect your information from being stolen, Nightly has not connected to this website. Learn more… The certificate is not trusted because the issuer certificate is unknown. The server might not be sending the appropriate intermediate certificates. An additional root certificate may need to be imported. Error code: SEC_ERROR_UNKNOWN_ISSUER. This error is occurred in google chrome as well as mozilla firefox and this solution is common for windows 7,windows 8,windows 8.1,windows 10 also. Solution: 1.Click "add exception" option. 2.Finally the problem is fixed. 3.This is the only way to solve the error.