function check_required(f) {

req_message = "The following fields are required:\n\n";
req_return = true;
if (f.field_firstname.value == '') {
	req_message += "First Name\n";
	req_return = false;
}
if (f.field_lastname.value == '') {
	req_message += "Last Name\n";
	req_return = false;
}
if (f.field_email.value == '') {
	req_message += "Email address\n";
	req_return = false;
}
	if (req_return == false) {
		alert(req_message)
	}
	return(req_return);
}