anchor.diff:  </head>
   <body>
   
  -  <div class="container">
  -    <h1>Shopify App - Installation</h1>
  -    <h2>Please enter the "myshopify" domain of your store</h2>
  +  <main class="container" role="main">
  +    <header>
  +      <h1>Shopify App — Installation</h1>
  +      <p class="subhead">
  +        <label for="shop">Please enter the “myshopify” domain of your store</label>
  +      </p>
  +    </header>
   
       <div class="container__form">
         <form method="GET" action="login">
  -        <input type="text" name="shop" placeholder="blabla.myshopify.com"/>
  -        <button type='submit'>Install</button>
  +        <input type="text" name="shop" id="shop" placeholder="blabla.myshopify.com"/>
  +        <button type="submit">Install</button>
         </form>
       </div>
  -  </div>
  +  </main>
   
   </body>
   </html>
  
positive.code:       margin-bottom: 10px;
      }
  
      h2 {
        font-size: 17px;
        line-height: 32px;
        font-weight: 300;
  
negative.code: <!DOCTYPE html>
  <html lang="en">
  <head>
    <title>Shopify App — Installation</title>
  
    <style>
      html, body { padding: 0; margin: 0; }
  