[e] (0) Explain why summary= is discouraged now.

git-svn-id: http://svn.whatwg.org/webapps@3523 340c8d12-0b0e-0410-8428-c7bf67bfef74

index

@@ -70707,6 +70707,18 @@ time:empty { binding: <i title="">time</i>; }</pre>
   described in the <code><a href=#the-table-element>table</a></code> section should be used
   instead.</p>
 
+  <p class=note>Use of the <code title=attr-table-summary><a href=#attr-table-summary>summary</a></code> attribute is discouraged
+  because in practice it is poorly understood. Because the attribute
+  is not exposed in visual user agents, authors who have included it
+  have typically not been able to test it, and have therefore set the
+  attribute to values that are of no use to users of accessibility
+  tools. This has lead to accessibility tools introducing heuristics
+  to try to avoid exposing such usage of the attribute to users. Even
+  the few authors who have made the best use of the attribute have
+  often misused it, for example by including text that would in fact
+  be useful for all users, or that is redundant with other information
+  on the page separate from the table.</p>
+
   <p class=XXX>It has been suggested that the summary="" attribute
   should not be obsolete, and the working group may vote on the matter
   at some future point.</p>

source

@@ -83565,6 +83565,19 @@ time:empty { binding: <i title="">time</i>; }</pre>
   described in the <code>table</code> section should be used
   instead.</p>
 
+  <p class="note">Use of the <code
+  title="attr-table-summary">summary</code> attribute is discouraged
+  because in practice it is poorly understood. Because the attribute
+  is not exposed in visual user agents, authors who have included it
+  have typically not been able to test it, and have therefore set the
+  attribute to values that are of no use to users of accessibility
+  tools. This has lead to accessibility tools introducing heuristics
+  to try to avoid exposing such usage of the attribute to users. Even
+  the few authors who have made the best use of the attribute have
+  often misused it, for example by including text that would in fact
+  be useful for all users, or that is redundant with other information
+  on the page separate from the table.</p>
+
   <p class="XXX">It has been suggested that the summary="" attribute
   should not be obsolete, and the working group may vote on the matter
   at some future point.</p>