Comodo and Positive SSL certificates are very popular due to their very low cost. They are so inexpensive that you can buy a Positive SSL certificate for just less than $9 per year or $15 per 3 years. Since Google start pushing Web Administrators to install SSL on their websites, cheap Comodo and Positive SSL certificates are first choice of low traffic website and personal blog owners.
Installation of these Comodo and Postive SSL certificates are not difficult. However, it is possible that you end up having NET_ERR_CERT_AUTHORITY_INVALID error on some mobile browsers after installing them.
This error occurs when you don’t install Intermediate SSL Certificate on your web server. Intermediate certificates sit between an end entity certificate and a root certificate.
So, how to fix this error? Simple, install Intermediate certificate!
Comodo/Positive SSL sends you a compress file containing four files:
All you need to do is to open first three files (AddTrustExternalCARoot.crt, COMODORSAAddTrustCA.crt, COMODORSADomainValidationSecureServerCA.crt) one by one in Notepad or Notepad ++ or any other suitable text editor. Then copy their entire content and paste them in a new text file. So at the end, you will have a file with content of three certificates. Save the new file as Certificate.crt and install it on your web server.