explain

docs/_includes/css/forms.html

@@ -594,6 +594,7 @@
 {% endhighlight %}
 
   <h4>Optional icons with hidden <code>.sr-only</code> labels</h4>
+  <p>For form controls with no visible label, add the <code>.sr-only</code> class on the label. Bootstrap will automatically adjust the position of the icon once it's been added.</p>
   <div class="bs-example">
     <div class="form-group has-success has-feedback">
       <label class="control-label sr-only" for="inputSuccess5">Hidden label</label>