Position.Window = {
    getDeltas: function() {
        var deltaX = window.pageXOffset
                || document.documentElement.scrollLeft
                || document.body.scrollLeft
                || 0;
        var deltaY = window.pageYOffset
                || document.documentElement.scrollTop
                || document.body.scrollTop
                || 0;
        return [deltaX, deltaY];
    }
}

function feedback() {
    var _scroll = Position.Window.getDeltas();
    var moveX = 840 + _scroll[0];
    var moveY = 120 + _scroll[1];
    new Effect.Move('MiniLightBoxContainer', { x: moveX, y: moveY, mode: 'absolute' });
}

new PeriodicalExecuter(feedback, 1);