ok ho risolto, ora funge!
inputField=nome_del_form
codice:
function refreshPreview(inputField,outputField,httpUrl)
{
var myText = "";
for (i=0;i<document.getElementById(inputField).length;i++)
{
myText = myText+document.getElementById(inputField).elements[i].name+"="+escape(document.getElementById(inputField).elements[i].value);
if (i<document.getElementById(inputField).length) {myText = myText+"&";}
}
if(window.XMLHttpRequest) {
xmlhttp = new XMLHttpRequest();
} else if(window.ActiveXObject) {
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
} else {
return false;
}
xmlhttp.open("POST", httpUrl, true);
xmlhttp.setRequestHeader("Content-type","application/x-www-form-urlencoded");
xmlhttp.setRequestHeader("Content-length",myText.length);
xmlhttp.setRequestHeader("Connection","close");
xmlhttp.onreadystatechange=function() {
if (xmlhttp.readyState == 4) {
document.getElementById(outputField).innerHTML = xmlhttp.responseText;
}
}
xmlhttp.send(myText);
}