That is a problem with that server because it doesn't send a required intermediate certificate (VeriSign Class 3 International Server CA - G3).

You can find the VeriSign intermediate certificates on the VeriSign site and save the code to a text file and use File > Open File to install the certificate.

You need the second certificate from this page.

• https://www.verisign.com/support/verisign-intermediate-ca/secure-site-pro-intermediate/index.html

On this page there are two other intermediate certificates (Class 3 CA - G2 and G3)

• https://www.verisign.com/support/verisign-intermediate-ca/secure-site-intermediate/index.html

Thanks for your reply. So I install second certificate is fine? We are using Secure Site https://knowledge.verisign.com/support/ssl-certificates-support/index?page=content&id=AR1409

I got the wrong certificate the first time, I hadn't tested it and I edited my above to give a link to the correct certificate.

It is the second certificate on this page (Secondary SSL Intermediate CA Certificate):

• https://www.verisign.com/support/verisign-intermediate-ca/secure-site-pro-intermediate/index.html

You can inspect the certificate chain via a site like this:

• http://www.networking4all.com/en/support/tools/site+check/

Thanks for provide useful website. Don't understand why will using secure-site-pro secondary cert but it is work. SSL Certificate correctly installed. Thanks again.

You're welcome.

Firefox will store intermediate certificates automatically if you visit a site that sends them, so if you haven't yet visited a site that has send it and then visit a site that doesn't send it, like in your case, then you get that SSL certificate error.