Add HTML before "Custom Elements"

index.html

@@ -2948,7 +2948,7 @@ <h2>Definition of Roles</h2>
 				<p>A nameless container <a>element</a> that has no semantic meaning on its own.</p>
 				<p>Contrast with <rref>group</rref>, which semantically groups its descendants in a named container.</p>
 				<p>A <code>generic</code> can provide a limited number of accessible states and properties for its descendants, such as <sref>aria-hidden</sref> and <pref>aria-live</pref>.</p>
-				<p class="note"><code>generic</code> is a superclass role used for the ontology. With the exception of providing <code>generic</code> <a href="https://html.spec.whatwg.org/multipage/custom-elements.html">Custom Elements</a>, authors should not use this role in content.</p>
+				<p class="note"><code>generic</code> is a superclass role used for the ontology. With the exception of providing <code>generic</code> <abbr title="Hypertext Markup Language">HTML</abbr> <a href="https://html.spec.whatwg.org/multipage/custom-elements.html">Custom Elements</a>, authors should not use this role in content.</p>
 				<p class="ednote">A triage of global properties is pending. This will reduce the number of inherited states and properties in the characteristics table below. For details, see <a href="https://github.com/w3c/aria/issues/999">issue #999</a>.</p>
 			</div>
 			<table class="role-features">