Custom Errors Web.config Script manager ASP.NET C# Ajax

<form id="form1" runat="server">

 <asp:ScriptManager ID="ScriptManager1" runat="server" OnAsyncPostBackError="ScriptManager1_AsyncPostBackError" AllowCustomErrorsRedirect="true"></asp:ScriptManager>

</form>

web.config

<system.web>

<customErrors mode="On" defaultRedirect="ErrorPage.aspx">

      <error statusCode="404" redirect="ErrorPage.aspx"/>

      <error statusCode="500" redirect="ErrorPage.aspx"/>

    </customErrors>

</system.web>

reference:- http://www.codedigest.com/Articles/ASPNETAJAX/115_Error_Handling_in_ASPNet_Ajax_Applications.aspx