function keepAlive() {
    try {
        var request = getWebRequest("GET", "KeepAlive.aspx?nc=" + (new Date()).getMilliseconds());
        if (request) {
            request.add_completed(onKeepAliveCompleted);
            request.invoke();
        }
    } catch(e) {
    }
}
function onKeepAliveCompleted(executor, eventArgs) {
}
window.setInterval(function(){keepAlive();}, 180000);