Editorial: clarify custom elements (#414)

Editorial: clarify custom elements
- clarifies when naming prohibited is applicable
- clarifies that if not provided a role, then the custom elements will map to `generic`.

index.html

@@ -541,8 +541,12 @@ <h2 id="docconformance">
               <a>autonomous custom element</a>
             </th>
             <td>
-              Role exposed from author defined {{ElementInternals}}.
-              Otherwise <a>no corresponding role</a>.
+              <p>
+                Role exposed from author defined {{ElementInternals}}
+              </p>
+              <p>
+                Otherwise <code>role=<a href="#index-aria-generic">`generic`</a></code>
+              </p>
             </td>
             <td>
               <p>
@@ -552,7 +556,10 @@ <h2 id="docconformance">
               <p>
                 Otherwise, <a><strong>any `role`</strong></a>
               </p>
-              <p class="proposed addition"><a>Naming Prohibited</a></p>
+              <p class="proposed addition">
+                <a>Naming Prohibited</a> if exposed as the `generic` role, or if exposed
+                as another role which prohibits naming.
+              </p>
               <p>
                 Otherwise, <a data-cite="wai-aria-1.2#global_states">global `aria-*` attributes</a> 
                 and any `aria-*` attributes applicable to the allowed roles.
@@ -1158,7 +1165,7 @@ <h2 id="docconformance">
                 Role exposed from author defined {{ElementInternals}}
               </p>
               <p>
-                Otherwise <a>no corresponding role</a>
+                Otherwise <code>role=<a href="#index-aria-generic">`generic`</a></code>
               </p>
             </td>
             <td>
@@ -1182,7 +1189,9 @@ <h2 id="docconformance">
                 <a href="#index-aria-switch">`switch`</a>
                 or <a href="#index-aria-textbox">`textbox`</a>
               </p>
-              <p class="proposed addition"><a>Naming Prohibited</a></p>
+              <p class="proposed addition">
+                <a>Naming Prohibited</a> if exposed as the `generic` role.
+              </p>
               <p>
                 Otherwise, <a data-cite="wai-aria-1.2#global_states">global `aria-*` attributes</a> 
                 and any `aria-*` attributes applicable to the allowed roles.