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.