Use of Ogg formats in HTML5
, HTML5 video is not currently as widespread as Flash videos, though of recent rollouts of experimental HTML5-based video players on websites, DailyMotion is so far the only one to use Ogg Theora and Vorbis formats, which suggests an increasing early interest in adopting HTML5 video.
HTML5
XML documents must be served with an XML Internet media type (often called "MIME type") such as codice_2 or codice_3, and must conform to strict, well-formed syntax of XML. XHTML 5 is simply XML-serialized HTML 5 data (that is, HTML 5 constrained to XHTML's strict requirements, e.g., not having any unclosed tags), sent with one of XML media types. HTML that has been written to conform to both the HTML and XHTML specifications  and which will therefore produce the same DOM tree whether parsed as HTML or XML is known as Polyglot markup