function handle(delta) {
	if (delta > 0){
		backImage();
	}else {
		nextImage();
	}
}
function wheel(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 (delta)
		handle(delta);
	if (event.preventDefault)
		event.preventDefault()
	event.returnValue = false;
}
if (window.addEventListener)
	window.addEventListener('DOMMouseScroll', wheel, false);
window.onmousewheel = document.onmousewheel = wheel;