<a id="my_show_search_box_button" href="#" onclick="document.getElementById('my_show_search_box_button').style.display='block'; document.getElementById('my_optional_container').style.display='block';" >Display it</a>
    
  <div id="my_optional_container" class="my_optional_container" style="display:none">
    <!-- Hidden content here -->
    
  </div>