function changeFontsize(size) {
  var linkElements = document.getElementsByTagName('link');
  
  // Disabling and enabling stylesheets
  for (var i = 0; i < linkElements.length; i++) {
    if (linkElements[i].getAttribute('title')) {
      linkElements[i].disabled = true;
      if (linkElements[i].getAttribute('title') == size) {
        linkElements[i].disabled = false;
      }
    }
  }
  
  // Setting a cookie
  var expiration = new Date();
  var expirationOneYear = expiration.getTime() + (365 * 24 * 60 * 60 * 1000);
  expiration.setTime(expirationOneYear);
  document.cookie = 'fontsize='+ size +'; expires='+ expiration.toGMTString() +'; path=/;';
}