anchor.diff:  ----
   <section class="titlepage">
     <!-- h1 used for book title -->
  -  <h1>Book Title</h1>
  +  <h1 class="title">Book Title</h1>
     <!-- Whatever else goes on the title page: publishername, logo, etc. -->
   </section>
   ----
  
positive.code: ----
  <section class="index">
    <!-- optional h1 used for index titles -->
    <h1>Index Title</h1>
    <div class="indexdiv">
      <h2>A</h2>
      <dl>
        <dt class="indexentry">Aardvark, <a class="indexentry xref" href="ch01#aardvark">All about Aardvark</a></dt>
        <dd>
  
negative.code: ----
  <section class="preface">
    <!-- h1 used for all preface titles -->
    <h1 class="title">Preface Title</h1>
    <!-- Lots of preface content here -->
  </section>
  ----
  