title: Unknown server tag 'ajaxToolkit:CalendarExtender'.
body: <p>I get this error when trying to use the latest ajaxToolKit NET4.</p>
  
  <p>I've downloaded it, extracted it as described in the instructions and selected the dll  in the toolkit and its loaded ok.</p>
  
  <p>The code I've added is for a simple calender off a textbox using the extension calender</p>
  
  <pre><code>&lt;asp:TextBox ID="txtDateFrom" runat="server" CausesValidation="true" &gt;
  &lt;/asp:TextBox&gt;
  &lt;ajax:calendarextender  ID="ce1" runat="server" Format="dd-MM-yyyy" 
                   TargetControlID="txtStartDate" PopupPosition="Right" &gt;
  &lt;/ajax:calendarextender&gt;
  </code></pre>
  
  <p>Am I missing something obvious?</p>