//
// Wanneer verticale scroll-wheel gebruikt wordt scrollt het top-element
//

function handle(delta) { top.scrollBy(0,-90*delta) }

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;