anchor.diff:              })
           }
   
  +        function displayErrorOnFailure(response, indicator){
  +            indicator.conceal()
  +            var divError = $('errors')
  +            var myDIV = document.createElement('div');
  +            myDIV.innerHTML=response.responseText;
  +            var errorFromResponse = Builder.node('h4', {id:'error'}, "Error occurs during the request process. Status is "+ response.getStatus() + ". Caused by " + myDIV.getElementsByClassName('message')[0].innerHTML);
  +            divError.appendChild(errorFromResponse)
  +        }
   
           function executeAddSource(input) {
               var data = ''
  
positive.code:             href= href+"?"+data
              var lastRequest = new Ajax.Request(href,
              {
                  method: 'post'
              });
          }
  
  
negative.code:             href= href+"?"+data
              var deleteRequest = new Ajax.Request(href,
              {
                  method: 'post',
                  onFailure: function(response) {
                      displayErrorOnFailure(response, indicator)
                  }
              });
  
              return true;
  