AJAX control tool not functioning after changing of project type

I had change my project from C# ASP.NET empty web application (.NET Framework 4.5) over to C# ASP.NET web form application (.NET Framework 4.5). After changing over I realise that my AJAX control isn't working at all. Below is one part of my code of password strength ajax control. Do help me check if I did anything wrongly or forget to add something into it. Thanks!

<%@ Register assembly="AjaxControlToolkit" namespace="AjaxControlToolkit" tagprefix="asp" %> <asp:Content ID="Content1" ContentPlaceHolderID="ContentPlaceHolder1" runat="server"> <asp:ToolkitScriptManager ID="ToolkitScriptManager1" runat="server"> </asp:ToolkitScriptManager> <asp:PasswordStrength ID="PasswordStrength1" runat="server" TargetControlID="txtPassword" DisplayPosition="RightSide" StrengthIndicatorType="Text&quo ...