function setGratis(e) {
	var event = e || window.event;
	var gratis = event.value;
	var url = 'set_gratis.php';
	var params = 'gratis=' + gratis;
	var req;

	if (window.XMLHttpRequest)
		req = new XMLHttpRequest();
	else if (window.ActiveXObject) {
		try {
			req = new ActiveXObject('Msxml2.XMLHTTP');
		}
		catch(err) {
			req = new ActiveXObject('Microsoft.XMLHTTP');
		}
	}

	if (req) {
		req.open('POST', url, true);
		req.setRequestHeader('Content-Type', 'application/x-www-form-urlencoded');
		req.send(params);
		var button = document.getElementById('checkoutshipping');
		button.onclick = null;
	} else {
		alert('Problemy z utworzeniem w Twojej przeglądarce obiektu XMLHttpRequest (Mozilla, Opera, Safari) lub ActiveXObject (IE)');
	}
}