per il post basta cambiare la funzione in questo modo:
codice:
function xxx() {
var HTTPobj = new RSobj();
var postData = "?var1=value1&var2=value2& ... &varn = valuen";
HTTPobj.open("POST", "x.php", true);
HTTPobj.setRequestHeader("Method", "POST x.php HTTP/1.1");
HTTPobj.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
HTTPobj.setRequestHeader("Content-length", postData.length);
HTTPobj.setRequestHeader("Connection", "close");
HTTPobj.onreadystatechange = function() { cut }
//modifiche eventuali al documento
HTTPobj.send(postData);
}