anchor.diff:  
   *HTML element*: +<canvas>+
   
  -*Note*: Should include fallbacks for environments that don't support HTML5 or JavaScript (e.g., link or image).
  +*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*:
   
  
positive.code: 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
  
  13 August 2013: Third release of Working Draft
  
  
negative.code: == HTMLBook Specification: Working Draft (last updated 29 December 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]
  
  