rotator = function () {
    if (rotator.download) {
        new Ajax.Request('http://fotonowak.com.pl/rotator/home/random-url', {
            onSuccess: function(response) {
                rotator.buffer.src = response.responseText
                rotator.download = false
                rotator.delay(0.5)
            }
        });
    } else {
        if (rotator.buffer.complete) {
            $('rotator').src = rotator.buffer.src
            rotator.buffer = new Image()
            rotator.download = true
            rotator.delay(3)
        } else {
            rotator.delay(0.5)
        }
    }
}
rotator.buffer = new Image()
rotator.download = true

Event.observe(window, 'load', rotator);