function popup( url ) {

  var width  = 400; 

  var height = 500;

  var title  = "";

  var scroll = "";

  var left = Math.round((screen.availWidth-width)/2);

  var top = Math.round((screen.availHeight-height)/2);

  open( url,"","width="+width+",height="+height+",top="+top+",left="+left+","+scroll);

}