// validate een emailadres
function val_Email(s){
    var i = 0;
    var sLength = s.length;
    while ((i < sLength) && (s.charAt(i) != " ")) { i++; }
    if (i < sLength) { return false; }
	var i = 0;
    while ((i < sLength) && (s.charAt(i) != "@")) { i++; }
    if ((i >= sLength) || (s.charAt(i) != "@")) return false;
    else i += 2;
    while ((i < sLength) && (s.charAt(i) != ".")) { i++ }
    if ((i >= sLength - 1) || (s.charAt(i) != ".")) return false;
    else return true;
}

//validate een verplicht in te vullen e-mailadres
function val_Emailneeded(email) {
	if(email.value != '') {
		if(!val_Email(email.value)) {
			alert('You didn\'t enter a valid e-mailaddress.');
			email.focus();email.select();return false;
		}
	} else {
		alert('You didn\'t enter an e-mailaddress');
		email.focus();email.select();return false;
	}
	return true;
}


//validate name
function val_name(name) {
	if(name.value == '') {
		alert('You didn\'t enter your name.');
		name.focus();return false;
	}
	return true;
}


//validate your feedback
function val_feedback(feedback) {
	if(feedback.value == '') {
		alert('Please send us your feedback.');
		feedback.focus();return false;
	}
	return true;
}