Event.observe(window, "load", function() {
for(var i=0; i<document.forms.length; i++) {
      Event.observe(document.forms[i], "submit", function(event) {
        var form = Event.element(event);
        if (form._submitted) {
            Event.stop(event);
        } else {
            form._submitted = true;
        }
      
    }, false);
}
  });