title: div after a div which position is fixed in css
body: <p>I have made a div and I have given it position: fixed using this style sheet:</p>
  
  <p><strong>CSS</strong></p>
  
  <pre><code>position: fixed;
  top: 35px;
  z-index: 9999;
  height:60px;
  background:#000;
  width:100%;
  </code></pre>
  
  <p>Now what I want is:
  if this div has height zero, then the div which is just after should come in place of the above div.
  if the height of div is not zero, the next div after this div should have a margin from the above div so both div will not overlap each other.</p>