Index: source
===================================================================
--- source	(revision 2950)
+++ source	(revision 2951)
@@ -18876,7 +18876,7 @@
    </dd>
 
 
-   <dt>Images whose contents are not known</dt>
+   <dt id="unknown-images">Images whose contents are not known</dt>
 
    <dd>
 
@@ -19116,6 +19116,19 @@
 
   </diV>
 
+  <div class="impl">
+
+  <h6>Guidance for conformance checkers</h6>
+
+  <p>Conformance checkers must report the lack of an <code
+  title="attr-img-alt">alt</code> attribute as an error unless the
+  conditions listed above for <a href="#unknown-images">images whose
+  contents are not known</a> or they have been configured to assume
+  that the document is an e-mail or document intended for a specific
+  person who is known to be able to view images.</p>
+
+  </div>
+
 
 
   <h4>The <dfn><code>iframe</code></dfn> element</h4>