function open_window(link, window_name, width, height, resizable, scrollbars) 
{ 
	return window.open(link, window_name,'toolbar=no,location=no,status=no,menubar=0,scrollbars='+scrollbars+',resizable='+resizable+',height='+height+',width='+width+',top='+(screen.height-height)/2+',left='+(screen.width-width)/2+',copyhistory=no');
}