title: Window.external is giving error "Unable to get property "xxx" of undefined or null reference"
body: <p>I am doing a window application in vs 2013 c# with an embedded webbrower. When window.external.xxx('1') is called from html displayed in the browser I am getting error </p>
  
  <blockquote>
    <p>"Unable to get property "xxx" of undefined or null reference".</p>
  </blockquote>
  
  <p>Webbrowser control version is 11.0.9600.17631. Any idea would be much appreciated. </p>
  
  <pre><code>&lt;input type="button" id="A1" value="good" onclick='window.exteranl.xxx("1");' /&gt;
  </code></pre>
  
  <p>What am I missing?</p>