SetFocusOnError property

One of the newer features in ASP.NET 2.0 which required more JavaScript code injection in the previous ASP.NET versions is to set focus on a certain server control on page load

this feature is now supported in ASP.NET 2.0 You can use the Page.SetFocus method to pass the ID of a control that should receive focus or you can call the Focus method on the control directly.

   1: Page.SetFocus("ControlID");

Also you can  set the DefaultFocus property of the Form element to the ID of a control that should receive focus when the page is first loaded

   1: <form id="formMain" runat="server" defaultfocus="control1">   

you can refer to the focus feature here http://quickstarts.asp.net/QuickStartv20/aspnet/doc/tipstricks/default.aspx#focusapi

This feature has a similar one for the validation controls you can use the validation control SetFocusOnError to whether focus is set to the control specified by the ControlToValidate property when validation fails.

   1: <asp:RequiredFieldValidator ID="RequiredFieldValidator1" runat="server" SetFocusOnError="true"  Display="Dynamic">

   2: </asp:RequiredFieldValidator>

   3: