Firefox "sec_error_unknown_issuer" error on geotrust SSL certificate

Problem: web site user getting in firefox (Chrome, IE don't show this error) when browsing https://. The intermediate SSl certificate is missing. Solution:

1. Download intermediate CA from Geotrust:
   • QuickSSL, QuickSSL Premium and SSL Trial Intermediate CA.
   • True Business ID with Extended Validation certificate.
2. 2- install it as CA cert for www.coachrider.com.2048.2010 SSL certificate

no more "sec_error_unknown_issuer" error.