Stackoverflow technology for push message?

I recommend using Source Source, unlike AJAX Comet, there is no open open connection, so you are much more capable of transferring more clients.

/* Event Source Code */
// Initial Startup
if (!!window.EventSource) {
    var source = new EventSource('EventSource.php');
    // Native EventSource Events
    source.addEventListener('open', function(e) {
        // Connection was opened.
    }, false);
    source.addEventListener('error', function(e) {
        if (e.readyState == EventSource.CLOSED) {
            // Connection was closed.
        }
    }, false);
    source.addEventListener('message', function(e) {
        // You'll have to make your own banner function here.
        // e.data, this is what you'll need.
    }, false);
}