added a warning about restricting zoom via content attribute

fixes w3c#602

sections/semantics-document-metadata.include

@@ -820,6 +820,19 @@
   The <dfn element-attr for="meta"><code>content</code></dfn> attribute gives the value of the
   document metadata or pragma directive when the element is used for those purposes. The allowed
   values depend on the exact context, as described in subsequent sections of this specification.
+
+  <div class="warning">
+
+  <p>Developers should not use the <code>user-scalable=no</code> or <code>maximum-scale=1.0</code>
+  values in the <a>content</a> attribute as their use hinders users ability to zoom the content to a size 
+  that is legible for their needs.</p>
+
+  <p>The use of these values could be appropriate in specific use cases, for map applications where 
+  zooming is handled via scripting or for a game application where a fixed viewport is required. 
+  In general their use will not be appropriate and therefore HTML conformance checking tools should 
+  display a warning.</p>
+
+  </div>
 
   If a <{meta}> element has a <dfn element-attr for="meta"><code>name</code></dfn>
   attribute, it sets document metadata. Document metadata is expressed in terms of name-value pairs,