/**
 * this function is called in loginbutton.tag.
 */
function onLogin(url) {
  var w = 800;
  var h = 400;
  var left = (screen.width/2)-(w/2);
  var top = (screen.height/2)-(h/2);
  window.open(url,"mywindow","width="+w+",height="+h+",left="+left+",top="+top);
}