missing class from the tutorial example

Difference between "We will be styling this page"
at https://github.com/codebar/tutorials/blob/master/html/lesson2/tutorial.md#today-we-will-be-focusing-on-fundamental-css-concepts
and "Download the files required to begin working through the tutorial from here(mac/linux) or here(windows)"
at https://gist.github.com/hundred/7332441/download

Author: stampycode

html/lesson2/example.html

@@ -20,8 +20,8 @@ <h2>Why do I like owls so much?</h2>
         <li>and lovely</li>
         <li>and cuddly</li>
       </ol>
-      <div><img src="images/img4.jpg" alt="cute owl"/></div>
-      <div><img src="images/img5.jpg" alt="another cute owl"/></div>
+      <div class="bigimg"><img src="images/img4.jpg" alt="cute owl"/></div>
+      <div class="bigimg"><img src="images/img5.jpg" alt="another cute owl"/></div>
       <a href="http://www.youtube.com/watch?v=gBjnfgnwXic">Watch this video here</a>
       <div id="the-quote">
         <h4>
@@ -45,10 +45,10 @@ <h3>Owls:</h3>
         </div>
         <ul id="links">
         <li>
-           <a href="mailto:social@codebar.io?subject=I love owls :: codebar">Email us</a>
+           <a href="mailto:social@codebar.io?subject=I love owls :: Codebar">Email us</a>
         </li>
         <li>
-           <a href="mailto:?subject=I love owls :: codebar">Email a friend</a>
+           <a href="mailto:?subject=I love owls :: Codebar">Email a friend</a>
         </li>
         <li>
           <a href="http://twitter.com/home?status=I love owls! via @codebar">Share your love of owls on twitter</a>