Author requirement: if a tab is active a corresponding tabpanel must be rendered (#2500)

Co-authored-by: Melanie Sumner <[email protected]>

Author: scottaohara

index.html

@@ -10205,6 +10205,7 @@ <h5>Presentational Role Inheritance</h5>
               for details on implementing a tab set design pattern.
             </p>
             <p>Authors MUST ensure [=elements=] with <a>role</a> <rref>tab</rref> are <a>accessibility children</a> of an element with the role <rref>tablist</rref>.</p>
+            <p>Authors MUST ensure that if a <code>tab</code> is active, a corresponding <code>tabpanel</code> that represents the active <code>tab</code> is rendered.</p>
             <p>Authors SHOULD ensure the <rref>tabpanel</rref> associated with the currently active tab is <a>perceivable</a> to the user.</p>
             <!-- keep following para synced with its counterpart in #tablist -->
             <p>
@@ -10438,7 +10439,7 @@ <h5>Presentational Role Inheritance</h5>
 
             <!-- keep following para synced with its counterpart in #tabpanel -->
             <p>
-              <rref>tablist</rref> elements are typically placed near usually preceding, a series of <rref>tabpanel</rref> elements. See the
+              <rref>tablist</rref> elements are typically placed near, and usually preceding, a series of <rref>tabpanel</rref> elements. See the
               <cite
                 ><a href="" class="practices"><abbr title="Accessible Rich Internet Applications">ARIA</abbr> Authoring Practices Guide</a></cite
               >
@@ -10544,7 +10545,7 @@ <h5>Presentational Role Inheritance</h5>
             </p>
             <!-- keep following para synced with its counterpart in #tablist -->
             <p>
-              <rref>tablist</rref> elements are typically placed near, usually preceding, a series of <rref>tabpanel</rref> elements. See the
+              <rref>tablist</rref> elements are typically placed near, and usually preceding, a series of <rref>tabpanel</rref> elements. See the
               <cite
                 ><a href="" class="practices"><abbr title="Accessible Rich Internet Applications">ARIA</abbr> Authoring Practices Guide</a></cite
               >