Connection is not secure
I am trying to run a thankyou page and I am getting a message from Firefox
Your connection is not secure
The owner of localhost has configured their web site improperly. To protect your information from being stolen, Firefox has not connected to this web site.
Report errors like this to help Mozilla identify and block malicious sites
localhost uses an invalid security certificate. The certificate is not trusted because it is self-signed. Error code: SEC_ERROR_UNKNOWN_ISSUER
Any ideas what can be done please?