function zwroc_cene(id) {
    
    var XMLHttpRequestObject = false;
    if(window.XMLHttpRequest) {
	XMLHttpRequestObject = new XMLHttpRequest();
    } else if (window.ActiveXObject) {
	XMLHttpRequestObject = new ActiveXObject("Microsoft.XMLHTTP");
    }
    var lista = document.getElementById('cennik');
    var rozmiar=parseInt(lista[lista.selectedIndex].value);
    var url="includes/zwroc_cene.php?rozmiar=" + rozmiar + "&id=" + id;
    var div=document.getElementById('div_cena');
    XMLHttpRequestObject.open("GET",url);
    XMLHttpRequestObject.onreadystatechange = function() {
        div.innerHTML = XMLHttpRequestObject.status;
    	if(XMLHttpRequestObject.readyState == 4 && XMLHttpRequestObject.status == 200) {
	    var str = XMLHttpRequestObject.responseText;
    	    div.innerHTML = str;
        }
    }
    XMLHttpRequestObject.send(null);
}