title: IE 8 & 9 try to download json response if using iframe
body: <p>I am using the blueimp fileUpload plugin to send files to the server and in ie 8 and ie 9 it tries to prompt me to download a file. When I open the file it is perfect json. </p>
  
  <p>I have tried setting the content type to text/plain as well as the dataType to text/plain but to no avail. </p>
  
  <p>I am using FubuMVC as well so I cant just return a string. If it is not json then it tries to render a view. </p>
  
  <pre><code>var obj = {
              dataType: 'json',
              contentType: "application/json",
              url: uploadUrl,
              formData: formData,
              start: function(e, data) {
                  $('#' + loadingDiv).dialog('open');
              },
              stop: function(e, data) {
                  $('#' + loadingDiv).dialog('close');
              },
              add: function(e, data) {
                  data.formData = obj.formData;
                  data.submit();
              },
  
              always: function(e, data) {
                  alert('done');
              }
          };
  
          $('#' + div).fileupload(obj);
  </code></pre>