/**
* Orginal: http://adomas.org/javascript-mouse-wheel/
* prototype extension by "Frank Monnerjahn" themonnie@gmail.com
*/
Object.extend(Event, {
    wheel: function (event){
        var delta = 0;
        if (!event) event = window.event;
        if (event.wheelDelta) {
            delta = event.wheelDelta/120;
            if (window.opera) delta = -delta;
        } else if (event.detail) {
            delta = -event.detail/3;
        }

        if (event.preventDefault) {
            event.preventDefault();
        }

        event.returnValue = false;
        return Math.round(delta); //Safari Round
    }
});