title: how can I apply css based on parent div class
body: <p>I have 2 div blocks similar to each other except their additional class. one have <code>desktop_version</code> and second have <code>mobile_version</code> class. now how I can apply css to child div of a div which have class with <code>mobile_version</code>. I am trying to achieve responsive design in doing so </p>
  
  <h2>mobileVersion</h2>
  
  <pre><code>&lt;div id="contactNumber_Wrapper" class="mobileVersion"&gt;
  
                      &lt;div class="contact-number"&gt;
                          &lt;i class="fa fa-phone"&gt;&lt;/i&gt;
                          &lt;span&gt;+44 02078062629&lt;/span&gt;
                          &lt;span class="outer-strip"&gt;&lt;/span&gt;
                      &lt;/div&gt;
  &lt;/div&gt;
  </code></pre>
  
  <h2>desktop-version</h2>
  
  <pre><code>&lt;div id="contactNumber_Wrapper" class="desktop_version"&gt;
  
                  &lt;div class="contact-number"&gt;
                      &lt;i class="fa fa-phone"&gt;&lt;/i&gt;
                      &lt;span&gt;+44 02078062629&lt;/span&gt;
                      &lt;span class="outer-strip"&gt;&lt;/span&gt;
                  &lt;/div&gt;
  
  &lt;/div&gt;
  </code></pre>
  
  <h2>css</h2>
  
  <p>??????</p>