Polyglot markupとは 意味・読み方・使い方

Polyglot markup is HTML that has been written to conform to both the HTML and XHTML specifications. A polyglot document can therefore be parsed as either HTML or XML, and will produce the same DOM structure either way. For example, in order for an HTML5 document to meet these criteria, the two requirements are that it must have an HTML5 doctype, and be written in well-formed XHTML. The same document can then be served as either HTML or XHTML, depending on browser support and MIME type.