new Event.observe(window, 'load', function(event) {
    form = $('SubscribeForm');
    
    //preloading button image & double-submit locking
    var sent = false;
    submitInactiveImage = new Image();
    submitInactiveImage.src = basePath+'/images/zapisz_black.gif';
    
    form.onsubmit = function() {
        $('submitSend').writeAttribute('src', basePath+'/images/zapisz_black.gif');
        if (sent) {
            return false;
        }
        sent = true;
    };
});