title: How to apply style only to particular screen type in bootstrap
body: <p>I have a general style definition as</p>
  
  <pre><code>.main-site-nav li a {
      padding-left: 0;
  }
  </code></pre>
  
  <p>Now want to apply a different style only for <code>.main-site-nav li a</code> in extra small screens (xs) only as follows.</p>
  
  <pre><code>/* xs screens only */
  .main-site-nav li a {
      padding-left: 15;
  }
  </code></pre>
  
  <p>How can I do it?</p>
  
  <p>Thanks</p>