Whenver a URL request is made, Web server creates instance of requested web form, generates HTML and posts it to browser for rendering. It then destroys instance of web form on the server. When user submits data back to the web server, a new instance of web form is created which has no knowledge of earlier webform. Hence conventional web page is stateless. In ASP.NET before web form get destroyed the state of the webform is stored in Viewstate(hidden control) on the page and when the page is posted back, the state of the webform is restored from view state.