<!--
function checkform ( form )
{
  // see http://www.thesitewizard.com/archive/validation.shtml
  // for an explanation of this script and how to use it on your
  // own website

  // ** START **
  if (form.naam.value == "") {
    alert( "Gelieve uw naam in te vullen." );
    form.naam.focus();
    return false ;
  }
  
  if (form.voornaam.value == "") {
    alert( "Gelieve uw voornaam in te vullen." );
    form.voornaam.focus();
    return false ;
  }
  
  if (form.telefoon.value == "") {
    alert( "Gelieve uw telefoonnummer in te vullen." );
    form.telefoon.focus();
    return false ;
  }
  
  if (form.email.value == "") {
    alert( "Gelieve uw emailadres in te vullen." );
    form.email.focus();
    return false ;
  }
  
  // ** END **
  return true ;
}
//-->