function isEmail(str) {
  // are regular expressions supported?
  var supported = 0;
  if (window.RegExp) {
	var tempStr = "a";
	var tempReg = new RegExp(tempStr);
	if (tempReg.test(tempStr)) supported = 1;
  }
  if (!supported)
	return (str.indexOf(".") > 2) && (str.indexOf("@") > 0);
  var r1 = new RegExp("(@.*@)|(\\.\\.)|(@\\.)|(^\\.)");
  var r2 = new RegExp("^.+\\@(\\[?)[a-zA-Z0-9\\-\\.]+\\.([a-zA-Z]{2,3}|[0-9]{1,3})(\\]?)$");
  return (!r1.test(str) && r2.test(str));
}

function validateForm(frm)
{
	var name = document.getElementById('MFormNaam').value;
	var email = document.getElementById('MFormEmail').value;
	var telephone = document.getElementById('MFormTelefoonnr').value;
	var message = document.getElementById('MFormTest').value;
	var error_msg = 'Een of meer velden zijn niet ingevuld of niet juist ingevuld. Vul alle velden in om het bericht te kunnen versturen.';
	
	if(name == "") {
		alert(error_msg);
		return false;
	}
	if(email == "" || !isEmail( email )) {
		alert(error_msg);
		return false;
	}
	if(telephone == "") {
		alert(error_msg);
		return false;
	}
	if(message == "") {
		alert(error_msg);
		return false;
	} else {
		return true;
	}
}