title: CSS nth-child does not work
body: <p>I know this question has been asked many times but I can't figure out the problem anyway, so this is my html:</p>
  
  <pre><code>    &lt;table class="UMLTable"&gt;
          &lt;tr&gt;
              &lt;th&gt;Table&lt;th&gt;
          &lt;/tr&gt;
          &lt;tr&gt;
              &lt;td&gt;Attribute 1&lt;td&gt;
          &lt;/tr&gt;
          &lt;tr&gt;
              &lt;td&gt;Attribute 1&lt;td&gt;
          &lt;/tr&gt;
          &lt;tr&gt;
              &lt;td&gt;Attribute 1&lt;td&gt;
          &lt;/tr&gt;
          &lt;/tr&gt;
      &lt;/table&gt;
  </code></pre>
  
  <p>So why this line does not work:</p>
  
  <pre><code>.UMLTable td:nth-child(even){
      background-color:blue;
  }
  </code></pre>