If you do a scale-out deployment of the Microsoft Dynamics GP 2013 Web Client you may encounter trust relationship problems if you do not have the SSL certificates correctly installed:
An error occurred during session monitoring 'System.ServiceModel.Security.SecurityNegotiationException: Could not establish trust relationship for the SSL/TLS secure channel with authority 'sc1.domain.azurecurve.co.uk:48650'. ---> System.Net.WebException: The underlying connection was closed: Could not establish trust relationship for the SSL/TLS secure channel. ---> System.Security.AuthenticationException: The remote certificate is invalid according to the validation procedure.
In my test environment I was using locally created self-signed SSL certificates. The above error was produced until I exported and imported the certificate from the Session Central onto the Session Hosts and then did the same for the Session Host certificates onto the Session Central.