Update index.html

Author: scottaohara

index.html

@@ -14276,7 +14276,13 @@ <h4 id=att-popover>`popover`</h4>
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       <th>Comments</th>
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-        If specified on an element with an implicit role of `generic`, then the element's role instead maps to <a class="core-mapping" href="#role-map-group">`group`</a>.
+        <p>UAs MUST NOT expose a details relation between a `popover` and its invoking element under the following conditions:</p>
+        <ul>
+          <li>when the `popover` is the next immediate accessibility sibling to the invoking element,</li>
+          <li>when the element has a `popovertarget=hide` attribute value,</li>
+          <li>or when the element is a descendant of the `popover` and its `popovertarget` is set to the auto state.</li>
+        </ul>
+        <p>If specified on an element with an implicit role of `generic`, then the element's role instead maps to <a class="core-mapping" href="#role-map-group">`group`</a>.</p>
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