The Viewstate of an ASP.NET page is created during the page life cycle, and saved into the rendered HTML using in the “__VIEWSTATE” hidden HTML field. The value stored in the “__VIEWSTATE” hidden field is the result of serialization of two types of data: Any programmatic change of state of the ASP.NET page and its controls. (Tracking and “Dirty” items come into play here. This will be detailed later.) Any data stored by the developer using the Viewstate property described previously. This value is loaded during postbacks, and is used to preserve the state of the web page.