title: Selecting every 4th <div>
body: <p>I have a long line of DIVs and I need to change the padding on every 4th DIV using the nth-child selector, but I am having problems getting it to work at all.</p>
  
  <p>Here is my css:</p>
  
  <pre class="lang-css prettyprint-override"><code>.content_tab {
      width: 220px;
      height: 340px;
      margin-right: 20px;
      margin-bottom: 20px;
      float: left;
      background-color: #0F0;
  }
  .content_tab:nth-child(4){
      background-color: #F00;
      margin-right: 0px;
  }
  </code></pre>
  
  <p>and here is my HTML:</p>
  
  <pre class="lang-html prettyprint-override"><code>&lt;div class="content"&gt;
      &lt;div class="content_tab"&gt;&lt;/div&gt;
      &lt;div class="content_tab"&gt;&lt;/div&gt;
      &lt;div class="content_tab"&gt;&lt;/div&gt;
      &lt;div class="content_tab"&gt;&lt;/div&gt;
      &lt;div class="content_tab"&gt;&lt;/div&gt;
      &lt;div class="content_tab"&gt;&lt;/div&gt;
      &lt;div class="content_tab"&gt;&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Any ideas?</p>