function ValidateForm()
{

var valid = true;
var themessage = "Fill in: ";


if (document.forms[0].inf_persoonsnaam.value=="") {
themessage = themessage + "\n - Lastname";
valid = false;
}

if (document.forms[0].inf_voornaam.value=="") {
themessage = themessage + "\n - Firstname";
valid = false;
}


if (document.forms[0].inf_email.value=="") {
themessage = themessage + "\n - Email";
valid = false;
}


if (document.forms[0].inf_telefoon.value=="") {
themessage = themessage + "\n - Tel.";
valid = false;
}


if (valid == true) {
return true
}
else {
alert(themessage);
return false;
   }

}