function checkContact() {
	var frm = document.formulier;
	
	if( frm["betreft"].value == "" ) {
		alert("U dient het betreft veld in te vullen");
		frm["betreft"].focus();
		return false;
	} else if( frm["naam"].value == "" ) {
		alert("U dient uw naam in te vullen");
		frm["naam"].focus();
		return false;
	} else if( frm["email"].value == "" || ! isEmail(frm["email"].value) ) {
		alert("U dient een geldig e-mailadres in te vullen");
		frm["email"].focus();
		return false;
	}
	
	return true;
	
}

function isEmail(strEmail) {
	var AtSym    = strEmail.indexOf('@')
	var Period   = strEmail.lastIndexOf('.')
	var Space    = strEmail.indexOf(' ')
	var Length   = strEmail.length - 1
	
	if( AtSym < 1 || Period <= AtSym + 1 || Period == Length || Space != -1 )
	 return false;

	return true;
}