title: How to make height equal width with css
body: <p>How to make height equal width with css.</p>
  
  <p>I have HTML like that :</p>
  
  <pre><code>&lt;div style="width:900px;height:200px;"&gt;
  &lt;a style="display:block; float:left; width:35%; background:green"&gt;&lt;/a&gt;
  &lt;/div&gt;
  </code></pre>
  
  <p>Now, I'd like to make height of <code>a</code> element equal width (35%). How can I do that? Thank your help.</p>