anchor.diff:        
         if(event_id == 'epochs[0].descriptionText-id')
              xleft = 50;
  -      else if( event_id == 'epochs[1].descriptionText-id' )
  +      else 
              xleft =  Event.pointerX(event) - 60;         
  -      else if( event_id == 'epochs[2].descriptionText-id' )
  -           xleft =  Event.pointerX(event) + 300;         
  +      
          return xleft;
       }
       
  
positive.code:            all_cells_of_this_epoch_column[i].remove();
           }
           
           
         }
         else
           return false;
           
          
      }
      
      function deleteEpochFromBackEnd( epoch_index )
      {
         createStudy.deleteEpoch( epoch_index , function(responseStr)
  	   	{
               alert('deleted from backend : ' + responseStr);	   	
  	   	});
      }
      
      
      function selectAll(event)
      {
  
negative.code:     
      function registerAddInstructionLinks()
      {
        var all_instructionLinks = $$('.instructionLinks');
         
        for(var i = 0 ; i < all_instructionLinks.length ; i++ )
        {
          Event.observe(all_instructionLinks[i], 'click', addInstructions);   
        }
      }
      
      function unRegisterAddInstructionLinks()
      {
         var all_instructionLinks = $$('.instructionLinks');
         
        for(var i = 0 ; i < all_instructionLinks.length ; i++ )
        {
          Event.stopObserving(all_instructionLinks[i], 'click', addInstructions);   
        }
      }
      
  