function creaAjax(){
        var objetoAjax=false;
        try {
                /*Para navegadores distintos a internet explorer*/
                objetoAjax = new ActiveXObject("Msxml2.XMLHTTP");
        } catch (e) {
                try {
                        /*Para explorer*/
                        objetoAjax = new ActiveXObject("Microsoft.XMLHTTP");
                }catch (E) {
                        objetoAjax = false;
                }
        }
        
        if (!objetoAjax && typeof XMLHttpRequest!='undefined') {
                objetoAjax = new XMLHttpRequest();
        }
        return objetoAjax;
}

function FAjax (url,capa,valores,metodo){
        var ajax=creaAjax();
    var capaContenedora = document.getElementById(capa);

    ajax.open ('POST', url, true);
    ajax.onreadystatechange = function() {
                if (ajax.readyState==1) {
                        capaContenedora.innerHTML="<span class='txt_ajax'>Loading data...</span>";
                }else if (ajax.readyState==4){
                        if(ajax.status==200){
                                if(ajax.responseText.indexOf('Warning') == -1){
                                        capaContenedora.innerHTML=ajax.responseText;
                                }else{
                                        capaContenedora.innerHTML = "<span class='txt_ajax'>There has been any error, please try again later (1).</span>";
                                }
                        }else if(ajax.status==404){
                                capaContenedora.innerHTML = "<span class='txt_ajax'>There has been any error, please try again later (2).</span>";
                        }else{
                                capaContenedora.innerHTML = "<span class='txt_ajax'>There has been any error, please try again later (3).</span>";
                        }
                }
    }
    ajax.setRequestHeader('Content-Type','application/x-www-form-urlencoded');
    ajax.send(valores);
    return;
}