title: CSS display none for class name when alone
body: <p>I want to set the display option to none for a css class when it is alone but it also hides the element when it is used with another class. </p>
  
  <p>so here is how the html looks like when I want to show the biography class: </p>
  
  <pre><code>&lt;div class="user biography"&gt;
    &lt;p&gt;Content&lt;/p&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>and here I want the biography class to be set to <code>display:none</code> when it is alone (not with user class): </p>
  
  <pre><code>&lt;div class="biography"&gt;
    &lt;p&gt;should hide&lt;/p&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>but if I do : </p>
  
  <pre><code>.biography{
    display: none;
  }
  </code></pre>
  
  <p>it hides the biography class in both cases. How can I hide it when it is alone and not with user class?</p>