Check the certificate store for the browser you are using. Mozilla Firefox has its own. Internet Explorer and Chrome on Windows rely on the Windows certificate store.

http://windows.microsoft.com/en-us/windows-vista/view-or-man...

Details on what certificates come with your installation of Mozilla Firefox: https://www.mozilla.org/en-US/about/governance/policies/secu...

Your organization may add their own certificates as described below: https://www.utexas.edu/its/help/user-certs/817