function validar (f) {
	if (f.name_01.value=="") {
		alert ("Please fill in your name.");
		f.name_01.focus();
		return false;
	} else if (f.surn_01.value=="") {
		alert ("Please fill in your your surname.");
		f.surn_01.focus();
		return false;
	} else if (f.email.value=="") {
		alert ("Please fill in e-mail address.");
		f.email.focus();
		return false;
	}
	return true;
}