ecco il codice:
<html>
<head>
<title>Untitled Document</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>
<body bgcolor="#FFFFFF">
<form name="form" >
<input type="text" name="campo2">
<input type="text" onkeydown="this.form.campo2.value=this.value;" name="campo1" />
</form>
</body>
</html>