function switchDuo(show, hide){
	document.getElementById(show).style.display = 'block';
	document.getElementById(hide).style.display = 'none';
}

function scroll(ref, element, value){
	var div = document.getElementById(element);
	div.scrollTop+=value;

	opacity = new Fx.Style(element, 'opacity', {
		duration: 800, 
		transition: Fx.Transitions.linear,
		wait: false
	});

	opacity.set(0);
	opacity.start(1);
	
	if(div.scrollTop == 0){
		document.getElementById(ref+'_b').style.display = 'none';
		document.getElementById(ref+'_m').style.display = '';
	}
	else if(div.scrollTop == div.scrollHeight-value){
		document.getElementById(ref+'_m').style.display = 'none';
		document.getElementById(ref+'_b').style.display = '';
	}
	else{
		document.getElementById(ref+'_m').style.display = '';
		document.getElementById(ref+'_b').style.display = '';
	}

}