[ac] (0) Accessibility of <canvas> is not optional. (credit: sf)

git-svn-id: http://svn.whatwg.org/webapps@2868 340c8d12-0b0e-0410-8428-c7bf67bfef74

index

  elements (typically <code><a href=#the-h1,-h2,-h3,-h4,-h5,-and-h6-elements>h1</a></code>) and then styled using CSS and
  supporting technologies such as XBL.</p>

  <p>When authors use the <code><a href=#the-canvas-element>canvas</a></code> element, they should
  also provide content that, when presented to the user, conveys
  <p>When authors use the <code><a href=#the-canvas-element>canvas</a></code> element, they must also
  provide content that, when presented to the user, conveys
  essentially the same function or purpose as the bitmap canvas. This
  content may be placed as content of the <code><a href=#the-canvas-element>canvas</a></code>
  element. The contents of the <code><a href=#the-canvas-element>canvas</a></code> element, if any,

source

  elements (typically <code>h1</code>) and then styled using CSS and
  supporting technologies such as XBL.</p>

  <p>When authors use the <code>canvas</code> element, they should
  also provide content that, when presented to the user, conveys
  <p>When authors use the <code>canvas</code> element, they must also
  provide content that, when presented to the user, conveys
  essentially the same function or purpose as the bitmap canvas. This
  content may be placed as content of the <code>canvas</code>
  element. The contents of the <code>canvas</code> element, if any,