If you use AjaxControlToolkit you may get Parser Error Message: Unknown server tag ‘asp:ScriptManager’. erro.
Server Error in ‘/’ Application.
Parser Error
Description: An error occurred during the parsing of a resource required to service this request. Please review the following specific parse error details and modify your source file appropriately.
Parser Error Message: Unknown server tag ‘asp:ScriptManager’.
Source Error:
Line 2: <asp:Content ID=”Content1″ ContentPlaceHolderID=”ContentPlaceHolder1″ Runat=”Server”>
Line 4: <asp:ScriptManager ID=”ScriptManager1″ runat=”server”>
Line 5: </asp:ScriptManager>
You Add This blow Code in your Web Config File.