function getViewPortSize(){
	var viewportwidth;
	 var viewportheight;
 
	 // the more standards compliant browsers (mozilla/netscape/opera/IE7) use window.innerWidth and window.innerHeight
	 if (typeof window.innerWidth != 'undefined')
	 {
		  viewportwidth = window.innerWidth,
		  viewportheight = window.innerHeight
	 }
	 
	// IE6 in standards compliant mode (i.e. with a valid doctype as the first line in the document)
	 else if (typeof document.documentElement != 'undefined'
		 && typeof document.documentElement.clientWidth !=
		 'undefined' && document.documentElement.clientWidth != 0)
	 {
		   viewportwidth = document.documentElement.clientWidth,
		   viewportheight = document.documentElement.clientHeight
	 }

	 // older versions of IE
	 else
	 {
		   viewportwidth = document.getElementsByTagName('body')[0].clientWidth,
		   viewportheight = document.getElementsByTagName('body')[0].clientHeight
	 }
	 return [viewportwidth, viewportheight];
}

function showImg(url)
{		
	var vpsize = getViewPortSize();
	document.getElementById("viewer").style.left = ""+Math.round((vpsize[0] - 398)/2)+"px";
	document.getElementById("viewer").style.top = ""+Math.round((vpsize[1] - 398)/2)+"px";
	document.getElementById("viewerimg").innerHTML="<img width='398' height='398' src='"+url+"' />";
	document.getElementById("viewer").style.visibility="visible";
}
function hideImg(){
	document.getElementById("viewer").style.visibility="hidden";
}