title: python selenium unable to select element
body: <p>I'm trying to select below element in a webpage. </p>
  
  <pre><code>.active &gt; b:nth-child(1)
  </code></pre>
  
  <p>This is my code :</p>
  
  <pre><code>timbro = browser.find_element_by_css_selector('.active &gt; b:nth-child(1)')
  hover = ActionChains(browser).move_to_element(timbro)
  hover.perform()
  </code></pre>
  
  <p>This is part of the error I'm getting:</p>
  
  <blockquote>
    <p>Message: Unable to locate element: 
    {"method":"css selector","selector":".active > b:nth-child(1)"}"</p>
  </blockquote>
  
  <p>what I'm trying to do is activate a drop down menu so that I can click on another link.</p>
  
  <p><strong>HTML Snippet:</strong></p>
  
  <pre><code>&lt;li&gt;
      &lt;a href="#nogo" class="main-link active"&gt;&lt;b&gt;Menu iniziale&lt;/b&gt;&lt;/a&gt;
      &lt;ul style="display: block;" class="sub-links"&gt;
          &lt;li&gt;
              &lt;a href="#nogo" onclick="Esegui('anagrafica.php')"&gt;Anagrafica&lt;/a&gt;
          &lt;/li&gt;
          &lt;li&gt;
              &lt;a href="#nogo" onclick="Esegui('logout.php')"&gt;Fine sessione&lt;/a&gt;
          &lt;/li&gt;
          &lt;li&gt;
              &lt;a href="#nogo" onclick="Esegui('main.php')"&gt;Home&lt;/a&gt;
          &lt;/li&gt;
          &lt;li&gt;
              &lt;a href="#nogo" onclick="Esegui('timbraWFA.php')"&gt;Timbro&lt;/a&gt;
          &lt;/li&gt;
      &lt;/ul&gt;
  &lt;/li&gt;
  </code></pre>