anchor.diff:  ----
   The bootstrap script is served by the Vaadin servlet from inside the
   [filename]#vaadin-server# JAR.
  -
  -Vaadin, or more precisely GWT, requires an invisible history frame, which is
  -used for tracking the page or fragment history in the browser.
  -
  -
  -[source, html]
  -----
  -  <iframe tabindex="-1" id="__gwt_historyFrame"
  -          style="position: absolute; width: 0; height: 0;
  -                 border: 0; overflow: hidden"
  -          src="javascript:false"></iframe>
  -----
   
   endif::web[]
   
  
positive.code: Embedding an UI requires the following basic tasks:
  
  * Set up the page header
  * Include a GWT history frame in the page
  * Call the [filename]#vaadinBootstrap.js# file
  * Define the [literal]#++<div>++# element for the UI
  * Configure and initialize the UI
  
negative.code:   <!-- Loads the Vaadin widget set, etc. -->
    <script type="text/javascript"
            src="VAADIN/vaadinBootstrap.js"></script>
  
    <h1>Embedding a Vaadin UI</h1>
      
  