When a user clicks the browser's Back button, the browser navigates through previously-viewed URLs, which can include URLs that contain history-point state data. If client code in the Web page detects that the URL contains history state data, it makes a request to the server page. This acts as a postback event, and the ScriptManagerProxy server control raises the Navigate event. You can handle this event and re-create the page as required in the Web application by using the state data that is passed with the event.