Added potential verb forms.

conjugation/drill.html

@@ -16,6 +16,11 @@
         <input id="numQuestions" value="10">
       </div>
       <button id="go">Go</button>
+
+      <div><small>
+        The quiz refers to negative て forms. In this test, they are assumed to be ～なくて  and not  ～ないで .
+      </small></div>
+
     </div>
 
     <div id="scoreSection">