anchor.diff:  If no content model or attribute requirements are explicitly specified, then HTMLBook adopts the corresponding requirements in the http://www.w3.org/html/wg/drafts/html/master/[HTML5 Specification]
   
   === Revision History and Notes
  +
  +29 December 2013: Minor revisions for clarity
   
   13 August 2013: Third release of Working Draft
   
  
positive.code: == HTMLBook Specification: Working Draft 13 August 2013
  
  Requirements for HTML5 elements in the HTMLBook specification are below. Special semantic inflections for +data-type+ attributes, unless otherwise noted, come from http://idpf.org/epub/vocab/structure/[EPUB 3 Structural Semantics Vocabulary]
  
  
negative.code: 
  *HTML element*: +<canvas>+
  
  *Notes*: Should include fallbacks for environments that don't support HTML5 or JavaScript (e.g., link or image). 
  You may include +<script>+ elements in your HTMLBook document +<head>+ elements to include/reference JS code for
  Canvas handling.
  
  *Examples*:
  
  