After installing web components of NAV 2013 Beta you will could receive the following error
Error: Could not load type System.ServiceModel.Activation.HttpModule
Solution:
Run aspnet_regiis.exe -iru
You will find this in the Windows/.NET
Details:
http://social.msdn.microsoft.com/Forums/en/wcf/thread/39571e42-aca7-469d-8c68-aa59c2da4fcc