function emailPage() {
  var messageText = 'Hello, I found a great web page at ' + window.location;
  var subjectText = 'Check out this Website';
  var email = prompt("Enter your friend's email address:", '');
    window.location = 'mailto:' + email +
      '?subject=' + encodeURIComponent(subjectText) +
      '&body=' + encodeURIComponent(messageText);
  }