title: imagebutton gives me error: [Accessibility] Missing contentDescription attribute on image
body: <p>[Accessibility] Missing contentDescription attribute on image</p>
  
  <p>What does this error mean and how can I fix it?</p>
  
  <pre><code>&lt;ImageButton
      android:id="@+id/callbannerbuttonpg1"
      android:layout_width="fill_parent"
      android:layout_height="wrap_content"
      android:layout_marginTop="157dp"
      android:background="@null"
      android:src="@drawable/callbanner"
      android:visibility="invisible" /&gt;
  </code></pre>