title: Unknown server tag 'cc1:AsyncFileUpload'
body: <p>I've recently downloaded Ajax Control Toolkit to use with my ASP.NET web app.
  I added the AsyncFileUpload control to a web form but when I try to run the application, I get an error :</p>
  
  <pre><code>"Unknown server tag 'cc1:AsyncFileUpload'." 
  </code></pre>
  
  <p>I have this in the ".aspx" page :</p>
  
  <pre><code>&lt;%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="cc1"    %&gt;
  </code></pre>