To connect to a https web server you need it's certificate or the certificate of the issuer CA. This/these will be sent to the browser upon connecting to the server. The browser will check them, if they are valid.
It's not essential that you install these certificates to your browser/system as trusted, but recommended.
Unfortunaltely Mozilla doesn't handle 16kbit certificates correctly, which we use for our Root CA,
so you have to install the CA-s certificate before you can connect to our https web server with Firefox or Seamonkey until this "bug" is fixed.
[Update: This is not a bug, this is a feature, ...or so they say:) ]
If you didn't install the certificates correctly prior connecting to the server with https you will receive Error Code -8182 in Firefox 2.
Our certificates can be found here.
Here is some tutorial how to install these certificates:
IE 7
Firefox
Opera 9
You can check the installed certificates in your system with mmc:

Heres a
Certificate Chain generator package.