Ajax control toolkit

Hi , I have download Ajax control toolkit 4 and did the following steps:

http://www.asp.net/ajaxlibrary/act.ashx

<%@ Page Title="" Language="C#" MasterPageFile="~/Site1.Master" AutoEventWireup="true" validateRequest="false"  CodeBehind="default.aspx.cs" Inherits="testingAuthentication._default" %><%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="asp" %><%@ Register TagPrefix="asp" Namespace="AjaxControlToolkit" Assembly="AjaxControlToolkit"%><%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit.HTMLEditor"
    TagPrefix="cc1" %><asp:Content ID="Content1" ContentPlaceHolderID="head" runat="server"></asp:Content><asp:Content ID="Content2" ContentPlaceHolderID="MasterContentPlaceHolder" runat="server"><asp:Panel ID="Panel1" runat="server"><cc1:Editor ID="Editor1" runat="server" /></asp:Panel></asp:Content>

now, when I run the programm , I am getting error, which saya that cannot find the source file.

can anybody help?