function win_open(str)
{
	w_wdt= 500; w_hgt= 500;
	add_w = window.open(str,'ch','top='+(screen.height-w_hgt)/2+',left='+(screen.width-w_wdt)/2+',width='+w_wdt+',height='+w_wdt+',scrollbars=0,status=0,resizable=1');
	add_w.focus(); if (add_w.opener == null) { add_w.opener = window; }
}