title: What does 'unspecified error' mean in IE?
body: <p>I'm getting <code>unspecified error</code> when reading <code>document.namespaces</code> in IE8.   </p>
  
  <p>I can't seem to reproduce the problem in a standalone page, my snippet is:</p>
  
  <pre><code>function addNamespace(key, value) {
    try {
      $("html").attr(key, value);
      if (document.namespaces &amp;&amp;  // This throws the error
        !document.namespaces[key]) {
        document.namespaces.add(key, value);
      }
    } catch (e) {
      alert("Error: " + e);
    }
  };
  </code></pre>
  
  <p>Never mind right now why I'm trying to add a namespace at runtime (it has to do with Facebook Like not working properly... see this comment - <a href="https://stackoverflow.com/questions/2957914/facebook-like-button-showing-in-firefox-but-not-showing-in-ie/2957944#comment9270143_2957944">Facebook like button showing in Firefox but not showing in IE</a>).</p>
  
  <p>My question is simple - on what conditions does <code>unspecified error</code> occur?</p>