function callInProgress (xmlhttp) {
    switch (xmlhttp.readyState) {
        case 1: case 2: case 3:
            return true;
            break;
        // Case 4 and 0
        default:
            return false;
            break;
    }
}

// Register global responders that will occur on all AJAX requests
Ajax.Responders.register({
    onCreate: function(request) {
        request['timeoutId'] = window.setTimeout(
            function() {
                // If we have hit the timeout and the AJAX request is active, abort it and let the user know
                if (callInProgress(request.transport)) {
                    request.transport.abort();
                    showFailureMessage();
                    // Run the onFailure method if we set one up when creating the AJAX object
                    if (request.options['onFailure']) {
                        request.options['onFailure'](request.transport, request.json);
                    }
                }
            },
            20000 // Five seconds
            );
    },
    onComplete: function(request) {
        // Clear the timeout, the request completed ok
        window.clearTimeout(request['timeoutId']);
    }
});