The web is state-less protocol, so the page gets instantiated, executed, rendered and then disposed on every round trip to the server. The developers code to add "statefulness" to the page by using Server-side storage for the state or posting the page to itself. When require to persist and read the data in control on webform, developer had to read the values and store them in hidden variable (in the form), which were then used to restore the values. With advent of .NET framework, ASP.NET came up with ViewState mechanism, which tracks the data values of server controls on ASP.NET webform. In effect, ViewState can be viewed as "hidden variable managed by ASP.NET framework!". When ASP.NET page is executed, data values from all server controls on page are collected and encoded as single string, which then assigned to page's hidden atrribute  "< input type=hidden >", that is part of page sent to the client.

 ViewState value is temporarily saved in the client's browser.ViewState can be disabled for a single control, for an entire page orfor an entire web application. The syntax is:
Disable ViewState for control (Datagrid in this example)
< asp:datagrid EnableViewState="false" ... / >
Disable ViewState for a page, using Page directive
< %@ Page EnableViewState="False" ... % >
Disable ViewState for application through entry in web.config
< Pages EnableViewState="false" ... / >