Event.observe(window, 'load', init, false);
function init() {
  Event.observe('zipForm', 'submit', checkZip);
}
function checkZip(e) {
  $('response').innerHTML = 'Sprawdzanie kodu pocztowego...';
  var pars = 'zip=' + escape($F('zip'));
  var myAjax = new Ajax.Updater('response', 'ajaxServer.php', {method: 'get', parameters: pars});
  Event.stop(e);
}