Prova cosi.
codice:
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Test tasto premuto</title>
<script type="text/javascript">
function pressione(evento)
{
var chiave;
if(!evento)
{
evento = window.event;
}
if(evento.keyCode)
{
chiave=evento.keyCode;
}
else
{
chiave=evento.charCode;
}
alert(chiave);
}
</script>
</head>
<body>
<input type="text" onkeypress="pressione(event)">
</body>
</html>