Assembly: System.Web.Mobile (in System.Web.Mobile.dll)
the control contains custom attributes and the current page does not allow custom attributes on controls.
This method notifies the server control that it should perform actions common to each HTTP request for the page it is associated with, such as setting up a database query. At this stage in the page lifecycle, server controls in the hierarchy are created and initialized, view state is restored, and form controls reflect client-side data.
Use the IsPostBack property to determine whether the page is being loaded in response to a client postback, or if it is being loaded and accessed for the first time.