What is an HTML Serialisation?
The HTML serialisation refers to the syntax of an HTML document defined in HTML5. The syntax is inspired by the SGML syntax from earlier versions of HTML, bits of XML (e.g. allowing a trailing slash on void elements, xmlns attributes), and reality of deployed content on the Web. Any document whose MIME type is determined to be text/html is considered to be an HTML serialization and must be parsed using an HTML parser.