function newAjax(){
        var xmlhttp=false;
        try { 
                xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
        } catch (e) {
                try {
                        xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
                } catch (E) {
                        xmlhttp = false;
                }
        }

        if (!xmlhttp && typeof XMLHttpRequest!='undefined') {
                xmlhttp = new XMLHttpRequest();
        }
        return xmlhttp;
}

function ajaxGET(url, id_contenedor){
        var contenedor = document.getElementById(id_contenedor);
        ajax=newAjax();
        ajax.open("GET", url ,true);
        ajax.onreadystatechange=function() {
                if (ajax.readyState==4) {
                        contenedor.innerHTML = ajax.responseText
                }
        }

         ajax.send(null)
}

function ajaxPOST(url, id_contenedor,datos){
        var contenedor = document.getElementById(id_contenedor);
        ajax=newAjax();
        ajax.open("POST", url ,true);
        ajax.onreadystatechange=function() {
                if (ajax.readyState==4) {
                        contenedor.innerHTML = ajax.responseText
                }
        }
        ajax.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
        ajax.send(datos)
}