//Detecta si el navegador acepta envios asíncronos
function detectar(){
    try {
        request = new ActiveXObject("Msxml2.XMLHTTP");
    } catch (e) {
        try {
            request = new ActiveXObject("Microsoft.XMLHTTP");
        } catch (E) {
            request = false;
        }
    }
    if (!request && typeof XMLHttpRequest!='undefined') {
        try {
	        request = new XMLHttpRequest();
        } catch (e) {
	        request=false;
        }
    }
    if (!request && window.createRequest) {
        try {
	        request = window.createRequest();
        } catch (e) {
	        request=false;
        }
    }
}