function popup(url, windowname, width, height, features){
	
	width=(width)?width:screen.width/2; 
	height=(height)?height:screen.height/2; 
	
	var screenX = (screen.width/2 - width/2); 
	var screenY = (screen.height/2 - height/2); 
	var features= "width=" + width + ",height=" + height +",scrollbars=yes,status=no"; 
	features += ",screenX=" + screenX + ",left=" + screenX; 
	features += ",screenY=" + screenY + ",top=" + screenY; 
	
	//var mywin = window.open(url, windowname, features); 
	var mywin = (window.open(url, windowname, features, false));
	if (mywin){ mywin.focus(); }
	return mywin;
	
}