title: IE is behaving differently when the web app is hosted on IIS 6, compared to IIS 7 & Cassini
body: <p>I have a web app that works fine from all browsers (IE9, Firefox, Chrome, Opera &amp; Safari) on my development machine . When I deploy the web app to a test server, IE will start to choke on a particular javascript component (Zoomify).</p>
  
  <p>I can have IE 9 open with the dev hosted web app in one tab and the test server web app in another tab and only the dev hosted app will work. The web app code is exactly the same on both machines, except for the web.config.</p>
  
  <p>The Developer Tools show both sites as being in <code>Browser Mode: IE9 Document Mode: IE9 standards</code>.</p>
  
  <p>The Zoomify component is failing on the following line:</p>
  
  <pre><code>c.onreadystatechange=null
  </code></pre>
  
  <p>with the error:</p>
  
  <pre><code>SCRIPT13: Type mismatch
  </code></pre>
  
  <p>What is going on here? Why is IE behaving differently with how it processes Javascript depending on where the web app is hosted?</p>
  
  <hr>
  
  <h1>Update</h1>
  
  <p>I've now tested on another server and strangely enough it is working. At this point, the situation is that when the web app is hosted on IIS 6, the javascript file will fail in IE.</p>
  
  <p>A similar issue exists in Opera, but I do not get an error message.</p>
  
  <pre><code>Dev Machine
  Windows 7
  Web Server: Cassini
  Status: Working
  
  Test Server 1
  Windows Server 2003
  Web Server: IIS 6.0
  Status: Not working
  
  Test Server 2
  Windows Server 2008
  Web Server: IIS 7.0
  Status: Working
  </code></pre>