Eccolo comunque:
codice:
<html>
<head>
<title>Dynamic Select Example</title>

<script type="text/javascript">
// Create arrays containing state cities
// Note: These arrays could be created dynamically
var arrStates, arrFlorida, arrNewYork, arrTennessee
arrFlorida = ["Daytona Beach", "Miami", "Orlando", "Tampa"]
arrNewYork = ["Albany","New York", "Oakland", "Rochester"]
arrTennessee = ["Gatlinburg", "Knoxville", "Memphis", "Nashville"]
arrStates =[arrFlorida, arrNewYork, arrTennessee]

// Function to handle dynamically altering the contents of the City List box
function handleChange(newDisplay)
{   var StateSelect, CitySelect, NumEntries, i
    StateSelect = document.frm.States
    CitySelect = document.frm.Cities

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

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

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

}
</script>
</head>

<body>
<form name="frm" action="">
States:
<select name="States" onChange="handleChange(this[this.selectedIndex].value)">
  <option value="-1">-- Select State --
  <option value="0">Florida
  <option value="1">New York
  <option value="2">Tennessee
</select>




Cities: 
<select name="Cities">
    <option value="-1">-- Select City --
    <option>
    <option>
    <option>
    <option>
</select>
<script type="text/javascript">
handleChange(-1)
</script>
</form>
</body>
</html>