<https://macmagazine.com.br/post/2009/02/16/are-my-sites-up-te-avisa-quando-sites-estao-fora-do-ar/>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://macmagazine.com.br/post/2009/02/16/are-my-sites-up-te-avisa-quando-sites-estao-fora-do-ar/>