What happens if I don't install intermediate certificates?
Failure to properly install intermediate certificates along with the issued SSL certificate means that the trusted-chain certificate cannot be established. This means that when visitors attempt to access your supposedly secure site, they will be presented with a "Security Alert" that indicates that "The security certificate was issued by a company you have not chosen to trust…" Faced with such a warning, potential customers will most likely take their business elsewhere.
Downloading and installing intermediate certificates on your Web server immediately fixes this problem. Intermediate certificates can be downloaded by clicking on the link embedded in the email message you'll receive upon certificate issuance.
Intermediate certificates are available as individual certificates and server specific certificate bundles. Please refer to the Installation Instructions to determine which intermediates you need. The intermediate certificates can be downloaded at the repository .