function showPopup(url) {

  var left = (screen.width) ? (screen.width - 340) / 2 : 0;

  var top = (screen.height) ? (screen.height - 500) / 2 : 0;

  var uniqueId = new Date().getTime();

  eval("page" + uniqueId + " = window.open(url, '" + uniqueId + "', 'toolbar=0, scrollbars=1, location=0, statusbar=1, menubar=0, resizable=0, width=340, height=500, left=' + left + ', top=' + top);");

}