function win_open(str)
{
 add_w = window.open(str,'ch','top='+(screen.height/2-600/2)+',left='+(screen.width/2-700/2)+',width=640,height=480,scrollbars=yes,status=no,resizable=yes');
 add_w.focus(); if (add_w.opener == null) { add_w.opener = window; }
}