function createRequest() {

    var request = null;

    try {
        request = new XMLHttpRequest();
    } catch (trymicrosoft) {
        try {
            request = new ActiveXObject("Msxml2.XMLHTTP");
        } catch (othermicrosoft) {
            try {
                request = new ActiveXObject("Microsoft.XMLHTTP");
            } catch (failed) {
                request = null;
            }
        }
    }
    if(request == null){
        alert("Erro ao criar o objeto request");
    }
    
    return request;
}