Hi, I am working on a Visual Web Part which requires creating a custom control. I am trying to add custom control to the same assembly as Visual Web Part and registering control as: <%@ Register TagPrefix="cus" Namespace="SomeCustomControlNameSpace" % When I am trying to access this its throwing runtime error : Unknown server tag 'cus:ControlName'. Do I need to make any Web.Config entry for this? Any Ideas?