How to detect online/offline event cross-browser?

I'm trying to accurately detect when the browser goes offline, using the HTML5 online and offline events.

Here's my code:

<script>
    // FIREFOX
    $(window).bind("online", applicationBackOnline); 
    $(window).bind("offline", applicationOffline);

    //IE
    window.onload = function() {
        document.body.ononline = IeConnectionEvent;
        document.body.onoffline = IeConnectionEvent;
    } 
</script>

It works fine when I just hit "Work offline" on either Firefox or IE, but it's kind of randomly working when I actually unplug the wire.

What's the best way to detect this change? I'd like to avoid repeating ajax calls with timeouts.