Ajax Editor Error

Question

hello,

 

I want use ajax Editor tool at my .net project. at first time it work fine, But after re-open my project  it not work. Please suggest me .

 

my code is................

 

 ..In header section-------------

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit.HTMLEditor"

TagPrefix="cc1" %>

 ---------in Body section-----------------

 

<cc1:Editor ID="EditorGuidline" runat="server" />