window.onload = function() {
		if (document.getElementById('contentscroll')){
				
			if ($('contentscroll').scrollHeight > $('contentscroll').offsetHeight) {
				Element.setStyle('track1', { visibility: 'visible' } );
				Element.setStyle('handle1', { visibility: 'visible' } );
				var sh = Math.ceil($('contentscroll').offsetHeight/$('contentscroll').scrollHeight*$('track1').getHeight());
				var aY = Math.ceil((sh-$('handle1').getHeight())/2);
			} else {
				var aY = 0;
			}
			// vertical slider control
			slider1 = new Control.Slider('handle1', 'track1', {
				alignY: eval(aY),
				axis: 'vertical',
				onSlide: function(v) { scrollVertical(v, $('contentscroll'), slider1);  },
				onChange: function(v) { scrollVertical(v, $('contentscroll'), slider1); }
			});
			

			// scroll the element vertically based on its width and the slider maximum value
			function scrollVertical(value, element, slider) {
				element.scrollTop = Math.round(value/slider.maximum*(element.scrollHeight-element.offsetHeight));
			}
			
			// disable vertical scrolling if text doesn't overflow the div
			if ($('contentscroll').scrollHeight <= $('contentscroll').offsetHeight) {
				slider1.setDisabled();
				$('track1').hide();
			} else {
				Element.setStyle('handle1', { height: sh+'px' } );
			}
			
			// mouse wheel code from http://adomas.org/javascript-mouse-wheel/
			function handle(delta) {
				slider1.setValueBy(-delta);
			}


			/** Event handler for mouse wheel event. */
			function wheel(event){
				var delta = 0;
					if (!event) /* For IE. */
						event = window.event;
					if (event.wheelDelta) { /* IE/Opera. */
						delta = event.wheelDelta/360;
					} else if (event.detail) { /** Mozilla case. */
						/** In Mozilla, sign of delta is different than in IE.
						* Also, delta is multiple of 3.
						*/
						delta = -event.detail/9;
					}
		
					/** If delta is nonzero, handle it.
					* Basically, delta is now positive if wheel was scrolled up,
					* and negative, if wheel was scrolled down.
					*/
					if (delta)
						handle(delta);
		
					/** Prevent default actions caused by mouse wheel.
					* That might be ugly, but we handle scrolls somehow
					* anyway, so don't bother here..
					*/
					if (event.preventDefault)
						event.preventDefault();
				
					event.returnValue = false;
			}

			// mozilla
			Event.observe('contentscroll', 'DOMMouseScroll', wheel);
			// IE/Opera
			Event.observe('contentscroll', 'mousewheel', wheel);
		}

}