In my earlier post I provided the step by step instructions to host a website in Apache web server and securing it thru HTTPS. I have found that site works perfectly fine in IE and Chrome but it throws certificate error while browsing it thru Mozilla. It throws the SEC_ERROR_UNKNOWN_ISSUER error.

If your application is calling APIs hosted on HTTPS endpoint then it may not work because Mozilla will block the API calls due to this error. So if API is returning some data then that data may not appear on the webpage.In this blog post we will resolve this issue.
STEP 1: Browse the site where this error is coming and download the certificate as per the below screenshot:
Also get the root certificate and intermediate certificates if it is not installed in your system.

STEP 2:In Firefox address bar type this : about:preferences#privacy
Now import certificates downloaded in step 1.

STEP 3: Now restart the browser and open the https enabled URL . You should not see SEC_ERROR_UNKNOWN_ISSUER certificate error and API calls will be successful.