anchor.diff:     
      <div class = "col-sm-6 col-md-3">
         <div class = "thumbnail">
  -         <img src = "/bootstrap/images/kittens.jpg" alt = "Generic placeholder thumbnail">
  +         
         </div>
         
         <div class = "caption">
  
positive.code:    
     <div class = "col-sm-6 col-md-3">
        <div class = "thumbnail">
           <img src = "/bootstrap/images/kittens.jpg" alt = "Generic placeholder thumbnail">
        </div>
        
        <div class = "caption">
  
negative.code:    
     <div class = "col-sm-6 col-md-3">
        <div class = "thumbnail">
           
        </div>
        
        <div class = "caption">
  