anchor.diff:    rest_request.onComplete = function(json_response) {
       document.getElementById("output").value = GenericUtils.html.escape (JSON.stringify(json_response, null, '  '))
     }
  -  rest_request.onError = function(xhr) { document.getElementById("output").innerHTML = "ERROR! " + JSON.stringify(xhr, null, '  ')
  +  rest_request.onError = function(xhr) {
  +    document.getElementById("output").innerHTML = "ERROR! " + JSON.stringify(xhr, null, '  ')
  +    document.getElementById("serverstatus").innerHTML = "Response error: " + xhr.statusText
  +    document.getElementById("serverstatus").style.visibility = "visible"
     }
     rest_request.onEnd = function(json_response) {
       console.log("end!")
  
positive.code:   }
    
    function send_form() {
      rest_request.request( JSON.parse( document.getElementById('form_request_str').value ) )
    }
  
    reset_form()
  
negative.code:           <h3>Server Response</h3>
          </div>
          <div class="panel-body">
            <div class="form-group">
            <textarea id="output" class="form-control" rows="16" style="resize: none;" readonly></textarea>
            </div>
            <div id="serverstatus" style="visibility: hidden;" class="alert alert-danger" role="alert">Error!</div>
          </div>
        </div>
      </div>
      
    </div>
  </div>
  
  
    <!-- Javascript -->
  