var position=0;

function doOnclicks(){
	a1=document.getElementById('backButton');
	a2=document.getElementById('fwdButton');
	a1.onclick = function(){scroll(-1);return false;}
	a2.onclick = function(){scroll(1);return false;}
}
function scroll(w){
	el = document.getElementById('image'+position);
	el.style.display='none';
	position = position + w;
	//edge
	m=getMax();
	if(position==-1)position=m;
	if(position==m+1)position=0;
	el = document.getElementById('image'+position);
	el.style.display='block';
}
function getMax(){
	i = getElementsByClassName(document,'li','images');
	return i.length-1;
}
addOnLoad(doOnclicks);