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