function changeContinent(){
 
   var index = document.getElementById('nazioni').selectedIndex;
   var paesi = new Array("","ITALY", "EUROPE","ASIA AND PACIFIC AREA","USA, NORTH and CENTRAL AMERICA");
 
   //alert(index);
   for(var i=1; i< paesi.length;i++)
   {
    if(i == index)
     document.getElementById(paesi[i]).style.display='block';
    else       
     document.getElementById(paesi[i]).style.display='none';
   }
}