title: No target for dynamic Modal Popup with Master Pages
body: <p>My dynamically added modal popup extender can't find the target control ID.  I'm using master pages.</p>
  
  <p><strong>EDIT:</strong> It works great without MasterPages.</p>
  
  <p>Web Form:</p>
  
  <pre><code>&lt;asp:Content ID="Content3" ContentPlaceHolderID="cphContent" runat="server"&gt;
      &lt;a runat="server" href="javascript:void(0);" ID="btnVote"&gt;vote&lt;/a&gt;
      &lt;asp:Panel ID="popScore" runat="server"&gt;&lt;/asp:Panel&gt;
  &lt;/asp:Content&gt;
  </code></pre>
  
  <p>CodeBehind</p>
  
  <pre><code>protected void Page_Load(object sender, EventArgs e)
  {
      ModalPopupExtender mpeScore = new ModalPopupExtender()
      {
          ID = "mpeSc",
          PopupControlID = popScore.ClientID,
          TargetControlID = btnVote.ClientID,
          BackgroundCssClass = "modalBackground",
          BehaviorID = "mpeScore"
      };
      this.Controls.Add(mpeScore);
  }
  </code></pre>
  
  <p>Error message is </p>
  
  <blockquote>
    <p>The TargetControlID of 'mpeSc' is not
    valid. A control with ID
    'ctl00_cphContent_btnVote' could not
    be found.</p>
  </blockquote>
  
  <p>I tried <code>btnVote.ID</code> also.  </p>