function win_open(str)
{
 add_w = window.open(str,'ch','top='+(screen.height/2-300/2)+',left='+(screen.width/2-400/2)+',width=420,height=350,scrollbars=0,status=no,resizable=yes');
 add_w.focus(); if (add_w.opener == null) { add_w.opener = window; }
}