ver_hover = 
  (((navigator.appName == "Netscape") && 
  (parseInt(navigator.appVersion) >= 3 )) || 
  ((navigator.appName == "Microsoft Internet Explorer") && 
  (parseInt(navigator.appVersion) >= 4 ))); 


if (ver_hover && document.images)
  {
   var indietroon  = new Image()
   indietroon.src  = "down_on.gif"
   var indietrooff = new Image()
   indietrooff.src = "down_off.gif"

   var avantion  = new Image()
   avantion.src  = "up_on.gif"
   var avantioff = new Image()
   avantioff.src = "up_off.gif"

   var indiceon  = new Image()
   indiceon.src  = "index_on.gif"
   var indiceoff = new Image()
   indiceoff.src = "index_off.gif"

   var homeon  = new Image()
   homeon.src  = "home_on.gif"
   homeoff     = new Image()
   homeoff.src = "home_off.gif"
  }

          
function on(imgName){
 if (ver_hover && document.images)
   document[imgName].src = eval(imgName + 'on.src')
}
          

function off(imgName) {
 if (ver_hover && document.images)
   document[imgName].src = eval(imgName + 'off.src')
}
 


function buildButton() {
    parametri = new Array()
    parametri[0] = new Array("Anni8991", "8991_off.gif", "8991_on.gif")
    parametri[1] = new Array("Anni9293", "9293_off.gif", "9293_on.gif")
    parametri[2] = new Array("Anni9495", "9495_off.gif", "9495_on.gif")
    parametri[3] = new Array("Anni9697", "9697_off.gif", "9697_on.gif")

    parametri[4] = new Array("Anni1998", "1998_off.gif", "1998_on.gif")
    parametri[5] = new Array("Anni1999", "1999_off.gif", "1999_on.gif")
    parametri[6] = new Array("Anni2000", "2000_off.gif", "2000_on.gif")
    parametri[7] = new Array("Anni2001", "2001_off.gif", "2001_on.gif")

    loadButton(parametri) 
}



imgButton = new Object();

function loadButton(arrayButton) {
 if (document.images) 
   {
    for (var i=0; i<arrayButton.length; i++) 
      {
       imgName = arrayButton[i][0] ;
       imgButton[imgName] = new Object();

       for (var j=1; j<arrayButton[i].length; j++) 
         {
          imgButton[imgName][j-1] = new Image(); 
          imgButton[imgName][j-1].src = arrayButton[i][j]; 
         }
      }
   }
}


function changeButton(imgName,i) {
 if (document.images) 
   {
    if (imgButton[imgName]) 
      {
       var img = document[imgName];
       if (img && typeof(imgButton[imgName][i].src) != "undefined") 
         { img.src = imgButton[imgName][i].src; }
         return true;
      }
   }
 return false;
}

buildButton()