function login_controlla(form) {

	var username = form.username.value;
	if (username == null || username == "") {
		window.alert("Inserisci la tua email.");
		form.username.focus();
		return false;
	}

	var password = form.password.value;
	if (password == null || password == "") {
		window.alert("Inserisci la tua password.");
		form.password.focus();
		return false;
	}
	
	return true;
}