codice:
<html>
<head>
<title></title>
<script type="text/javascript">
function userpass(f){
f.username.value=f.nome.value.toLowerCase().substr(0,1)
f.username.value+=f.cognome.value.toLowerCase()
f.password.value=f.nome.value.toLowerCase()
}
</script>
</head>
<body>
<form>
nome: <input type="text" name="nome" value="" onkeyup="userpass(this.form)" />

cognome: <input type="text" name="cognome" value="" onkeyup="userpass(this.form)" />

<hr />
username: <input type="text" name="username" value="" />

password: <input type="text" name="password" value="" />

</form>
</body>
</html>