function switchDiv(n) {
   var id;
   var hide = 0;
   switch(n) {
      case 1 : id = "venise"; break;
	  case 2 : id = "fleur"; break;
	  case 3 : id = "costa"; break;
     
      }
   if ( document.getElementById(id).style.display == "block" ) hide = 1;
   document.getElementById('venise').style.display = "none";
   document.getElementById('fleur').style.display = "none";
   document.getElementById('costa').style.display = "none";
   
   if ( hide != 1 ) document.getElementById(id).style.display = "block";
   }