grazie!
ho modificato il codice ma non funziona...ve lo posta...ke errore c'è??

codice:
<script type="text/javascript">
// Create arrays containing state cities
// Note: These arrays could be created dynamically
var arrLista, arrGold, arrSilver, arrBronze
arrGold = ["Reg 1", "Reg 2", "Reg 3", "Reg 4"]
arrSilver = ["Reg 5","Reg 6", "Reg 7", "Reg 8"]
arrBoronze = ["Reg 9", "Reg 10", "Reg 11", "Reg 12"]
arrLista =[arrGold, arrSilver, arrBronze]

// Function to handle dynamically altering the contents of the City List box
function handleChange(newDisplay)
{   var ListaSelect, RegaloSelect, NumEntries, i
    ListaSelect = document.frm.Lista
    RegaloSelect = document.frm.Regalo

  // Delete all entries in the cities list box
  for (i = RegaloSelect.length; i > 0; i--)
  {
    RegaloSelect.options[i-1] = null
  }

  // Add comment option to City List box
  RegaloSelect.options[0] = new Option("-- Seleziona Regalo --",0)

  // If state is selected add its cities to the City List box
  if (newDisplay >= 0)
  {
    NumEntries = arrLista[newDisplay].length
    for (i = 1; i <= NumEntries; i++)
    {
      RegaloSelect.options[i] = new Option((arrLista[newDisplay])[i-1],(i))
    }
  }
  RegaloSelect.selectedIndex = 0

}
</script>

<html>

<form name="frm">
<select name="Lista" onChange="handleChange(this[this.selectedIndex].value)">
  <option value="-1">-- Selezione Lista --
  <option value="0">Lista Gold
  <option value="1">Lista Silver
  <option value="2">Lista Bronze
</select>
<select name="Regalo">
    <option value="-1">-- Selezione Regalo --
    <option>
    <option>
    <option>
    <option>
</select>
<script type="text/javascript">
handleChange(-1)
</script>
</form>

</html>