function pop(url,name,x_win,y_win,features) {
  var wid=screen.width;
  var hei=screen.height;
  var from_top=hei/2-y_win/2;
  var from_left=wid/2-x_win/2;
  var specs = "height=" + y_win + ", width=" + x_win + ", top=" + from_top + ", left=" + from_left + " ," + features;
  var win = window.open(url,name,specs);
}