Update guidelines/index.html

not a definition, so adding relative link

guidelines/index.html

@@ -802,7 +802,7 @@ <h2>Change Log</h2>
                         <li>updated and corrected the <a href="#input-purposes">input purposes</a> list</li>
                         <li>modified the formatting of Target Size (Minimum) and Accessible Authentication (Minimum)</li>
                         <li>modified the visual presentation for content identified as New</li>
-                        <li>modified the language covering devices in the <a>Abstract</a></li>
+                        <li>modified the language covering devices in the <a href="#abstract">Abstract</a></li>
                         <li>made editorial changes to improve consistent use of definitions in the success criteria</li>
                         <li>made editorial changes to improve consistent use of the terms <q>success criteria/criterion</q>, <q>web</q>, <q>website</q>, and <q>web page</q></li>
                     </ul>