var xhr;
function create_xhr() {
    if (window.XMLHttpRequest) {
        xhr = new XMLHttpRequest;
    } else if (window.ActiveXObject) {
        xhr = new ActiveXObject("Microsoft.XMLHTTP");
    } else {
        alert("Cannot create XMLHttpRequest object.");
    }
}

function show_xhr_error() {
    alert("XMLHttpRequest error: " + "\n" + "Error code: " + xhr.status + "\n" + "Message: " + xhr.text);
}