function displayItemImage( isNext)
{
	var imgCount=0;
	while(true)
	{
		var itemImg=document.getElementById("itemimg"+(imgCount+1));
		if(itemImg==null)
		{
			break;
		}
		imgCount++;
	}
	if(imgCount==0)
	{
		return;
	}
	
	var firstImg=1;
	for(i=1;i<=imgCount;i++)
	{
		var itemImg=document.getElementById("itemimg"+i);
		if(itemImg.style.display!="none")
		{
			firstImg=i;
			break;
		}
	}
	if(isNext==0)
	{
		firstImg=(firstImg==1)?1:(firstImg-1);
	}
	else
	{
		firstImg=(firstImg>(imgCount-4)&&imgCount>4)?(imgCount-3):(firstImg+1);
	}
	
	var lastImg=document.getElementById("img"+(firstImg+3));
	if(lastImg==null)
	{
		return;
	}
	var imgSrc=lastImg.src;
	var isNoimage=imgSrc.indexOf("noimage");
	if(isNoimage>0)
	{
		var nxt=document.getElementById("nxtBtn");
		nxt.style.cursor="text";
		return;
	}
	for(i=1;i<=imgCount;i++)
	{
		var itemImg=document.getElementById("itemimg"+i);
		itemImg.style.display=(i>=firstImg && i<firstImg+4)?"block":"none";
	}
	
	var pre=document.getElementById("preBtn");
	if(firstImg<=1)
	{
		pre.style.cursor="text";
		pre.src="http://lib.store.yahoo.net/lib/eforcity/img-item-thum-backward-grey.gif"
	}
	else
	{
		pre.style.cursor="pointer";
		pre.src="http://lib.store.yahoo.net/lib/eforcity/img-item-thum-backward.gif"
	}
	
	var nxt=document.getElementById("nxtBtn");
	if(firstImg>(imgCount-4))
	{
		nxt.style.cursor="text";
		nxt.src="http://lib.store.yahoo.net/lib/eforcity/img-item-thum-forward-grey.gif";
	}
	else
	{
		nxt.style.cursor="pointer";
		nxt.src="http://lib.store.yahoo.net/lib/eforcity/img-item-thum-forward.gif";
	}
}