<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<http://schema.org/WebSite>
<https://www.zen-cart.com/showthread.php?192566-Can-I-force-html-with-every-email&s=b7bd2841f4c9f0af3ca4bf0589637445&p=1105207>