function validateForm(form) { 

if (form.name.value == "") { //This checks to make sure the field is not empty
   alert("Graag uw naam invullen."); //Informs user of empty field
   return false; //This prevents the form from being submitted
}

if (form.email.value == "" && form.telephone.value == "") { //This checks to make sure the field is not empty
   alert("Graag uw e-mail of telefoonnummer invullen."); //Informs user of empty field
   return false; //This prevents the form from being submitted
}




}