var popupwin=0
function popupwindow(urlstr,left,top,width,height)
{if(popupwin)
	{if(!popupwin.closed)popupwin.close();
	}
	popupwin=open(urlstr,'popupwin','toolbar=no,location=no,directories=no,status=no,menubar=no,scrollbars=yes,resizable=no,copyhistory=yes,width='+width+',height='+height+',left='+left+',top='+top+',screenx='+left+',screeny='+top+'');
}