anchor.diff:  <html lang="en">
   <head>
     <meta charset="utf-8" />
  +  <meta name="viewport" content="width=device-width, initial-scale=1">
     <title>Action Controller: Exception caught</title>
     <style>
       body {
  
positive.code:     }
  
      h1 {
        margin: 0.2em 0;
        line-height: 1.1em;
        font-size: 2em;
  
negative.code:     }
  
      .line.active {
        background-color: #FCC;
      }
  
      .button_to {
  