fix typo (#557)

Author: scottaohara

tests/selectedcontent.html

@@ -63,7 +63,7 @@ <h2>Tests:</h2>
 			<div class="widgetDemo">
 				<h3>Test 1</h3>
 				<p>
-                    Authors MUST NOT use any <code>role</code> or <code>aria-*</code> attribute on the <code>selectedcontent</code> attribute when it
+                    Authors MUST NOT use any <code>role</code> or <code>aria-*</code> attribute on the <code>selectedcontent</code> element when it
                     is a valid child of the <code>button</code> part of a customized <code>select</code> element. Additionally authors MUST NOT use ARIA 
                     attributes on the <code>button</code> part of a customized <code>select</code> element.</p>