[e] (0) clarify what 'focus' means

Fixing http://www.w3.org/Bugs/Public/show_bug.cgi?id=12214

git-svn-id: http://svn.whatwg.org/webapps@6097 340c8d12-0b0e-0410-8428-c7bf67bfef74

complete.html

   <p>When a <code><a href=#the-canvas-element>canvas</a></code> element <a href=#represents>represents</a>
   <a href=#embedded-content>embedded content</a>, the user can still focus descendants
   of the <code><a href=#the-canvas-element>canvas</a></code> element (in the <a href=#fallback-content>fallback
-  content</a>). This allows authors to make an interactive canvas
-  keyboard-focusable: authors should have a one-to-one mapping of
+  content</a>). When an element is focused, it is the target of
+  keyboard interaction events (even though the element itself is not
+  visible). This allows authors to make an interactive canvas
+  keyboard-accessible: authors should have a one-to-one mapping of
   interactive regions to focusable elements in the <a href=#fallback-content>fallback
-  content</a>.</p>
+  content</a>. (Focus has no effect on mouse interaction
+  events.) <a href=#DOMEVENTS>[DOMEVENTS]</a></p>
 
   <p>The <code><a href=#the-canvas-element>canvas</a></code> element has two attributes to control the
   size of the coordinate space: <dfn id=attr-canvas-width title=attr-canvas-width><code>width</code></dfn> and <dfn id=attr-canvas-height title=attr-canvas-height><code>height</code></dfn>. These

index

   <p>When a <code><a href=#the-canvas-element>canvas</a></code> element <a href=#represents>represents</a>
   <a href=#embedded-content>embedded content</a>, the user can still focus descendants
   of the <code><a href=#the-canvas-element>canvas</a></code> element (in the <a href=#fallback-content>fallback
-  content</a>). This allows authors to make an interactive canvas
-  keyboard-focusable: authors should have a one-to-one mapping of
+  content</a>). When an element is focused, it is the target of
+  keyboard interaction events (even though the element itself is not
+  visible). This allows authors to make an interactive canvas
+  keyboard-accessible: authors should have a one-to-one mapping of
   interactive regions to focusable elements in the <a href=#fallback-content>fallback
-  content</a>.</p>
+  content</a>. (Focus has no effect on mouse interaction
+  events.) <a href=#DOMEVENTS>[DOMEVENTS]</a></p>
 
   <p>The <code><a href=#the-canvas-element>canvas</a></code> element has two attributes to control the
   size of the coordinate space: <dfn id=attr-canvas-width title=attr-canvas-width><code>width</code></dfn> and <dfn id=attr-canvas-height title=attr-canvas-height><code>height</code></dfn>. These

source

   <p>When a <code>canvas</code> element <span>represents</span>
   <span>embedded content</span>, the user can still focus descendants
   of the <code>canvas</code> element (in the <span>fallback
-  content</span>). This allows authors to make an interactive canvas
-  keyboard-focusable: authors should have a one-to-one mapping of
+  content</span>). When an element is focused, it is the target of
+  keyboard interaction events (even though the element itself is not
+  visible). This allows authors to make an interactive canvas
+  keyboard-accessible: authors should have a one-to-one mapping of
   interactive regions to focusable elements in the <span>fallback
-  content</span>.</p>
+  content</span>. (Focus has no effect on mouse interaction
+  events.) <a href="#DOMEVENTS">[DOMEVENTS]</a></p>
 
   <p>The <code>canvas</code> element has two attributes to control the
   size of the coordinate space: <dfn