title: jQuery show/hide not working
body: <p>I have a basic html page with some JS and CSS:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>$('.expand').click(function() {
    $('.img_display_content').show();
  });</code></pre>
  <pre class="snippet-code-css lang-css prettyprint-override"><code>@charset "utf-8";
  
  /* CSS Document */
  
  .wrap {
    margin-left: auto;
    margin-right: auto;
    width: 40%;
  }
  
  .img_display_header {
    height: 20px;
    background-color: #CCC;
    display: block;
    border: #333 solid 1px;
    margin-bottom: 2px;
  }
  
  .expand {
    float: right;
    height: 100%;
    padding-right: 5px;
    cursor: pointer;
  }
  
  .img_display_content {
    width: 100%;
    height: 100px;
    background-color: #0F3;
    margin-top: -2px;
    display: none;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;html&gt;
  
  &lt;head&gt;
    &lt;link href="beta.css" rel="stylesheet" type="text/css" /&gt;
    &lt;script src="http://code.jquery.com/jquery-2.1.0.min.js"&gt;&lt;/script&gt;
  &lt;/head&gt;
  
  &lt;body&gt;
    &lt;div class="wrap"&gt;
      &lt;div class="img_display_header"&gt;
        &lt;div class="expand"&gt;+&lt;/div&gt;
      &lt;/div&gt;
      &lt;div class="img_display_content"&gt;&lt;/div&gt;
    &lt;/div&gt;
    &lt;/div&gt;
  &lt;/body&gt;
  
  &lt;/html&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>A click on the <code>div</code> with the class <code>expand</code> does nothing...
  I also have tried to copy/paste an example code from jQuery website but it also didn't work.
  Can anyone help me with this problem?</p>