ScriptManager.AddHistoryPoint Method (String, String)
Creates a history point and adds it to the browser's history stack, using the specified state key and state value.
Assembly: System.Web.Extensions (in System.Web.Extensions.dll)
Use this method to create a history point when you only want to save a value to identify the state. When you create a history point, serialized and encrypted data is appended to the URL of the Web page and an entry is included in the browser's history stack. The title of the Web page is used as the title of the state entry in the history stack.
You can use the state data to re-create the page when any subsequent server navigation event is raised. For more information, see Managing Browser History Using ASP.NET Server Controls.