title: Undefined Ext for ExtJs
body: <p>New to ExtJs. I have looked at a bunch of threads, but everything I try is not working.  I am using ExtJS 4 and  I keep getting and undefined Ext error for the following code:</p>
  
  <pre><code>&lt;html&gt;
  &lt;head&gt;
  
      &lt;script type="text/javascript" src="/extjs/ext-all.js"&gt;&lt;/script&gt;
      &lt;script type="text/javascript" src="app.js"&gt;&lt;/script&gt;
  &lt;/head&gt;
  &lt;body&gt;&lt;/body&gt;
  &lt;/html&gt;
  
  //app.js
  Ext.application({
      name: 'HelloExt',
      launch: function() {
          Ext.create('Ext.container.Viewport', {
              layout: 'fit',
              items: [
                  {
                      title: 'Hello Ext',
                      html : 'Hello! Welcome to Ext JS.'
                  }
              ]
          });
      }
  });
  </code></pre>