<https://blog.tremend.com/prototype-based-script-for-notifying-users-for-unsaved-changes-when-leaving-a-page/#primaryimage>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://blog.tremend.com/prototype-based-script-for-notifying-users-for-unsaved-changes-when-leaving-a-page/>