window.addEvent('domready', function(){ 
			  var totIncrement		= 0;
			  var increment			= 171;
				if(totIncrement == 0){
					document.getElementById('previous').style.display = "none";
				} 
			  var maxRightIncrement	= increment*(-41);
			  var fx = new Fx.Style('myList', 'margin-left', {
						duration: 1000,
						transition: Fx.Transitions.Back.easeInOut,
						wait: true
			   });
			   
			    
			   
			   //-------------------------------------
			  // EVENTS for the button "previous"
			  $('previous').addEvents({ 
				  'click' : function(event){ 
				  if(totIncrement<0){
							totIncrement = totIncrement+increment;
							fx.stop()
							fx.start(totIncrement);
							display(totIncrement, maxRightIncrement);
							
						}
					}			  	  
			  }); 
			 
			   //-------------------------------------
			  // EVENTS for the button "next"
			  $('next').addEvents({ 
				  'click' : function(event){ 
					 if(totIncrement>maxRightIncrement){
						 totIncrement = totIncrement-increment;
						fx.stop()
						fx.start(totIncrement);
						display(totIncrement, maxRightIncrement);
						
					}
				  }		  		  
			  })
				function display(totIncrement, maxRightIncrement){
					
					if(totIncrement== 0){
						document.getElementById('previous').style.display = "none";
						
					} else {
						document.getElementById('next').style.display = "block";
						document.getElementById('previous').style.display = "block";
					}
					if(totIncrement == maxRightIncrement){
					
						document.getElementById('next').style.display = "none";
						//document.getElementById('previous').style.display = "block";
					} else {
						//document.getElementById('previous').style.display = "block";
						document.getElementById('next').style.display = "block";
					}
				 
				}	
				
				
			  
			 
		});