title: Set width of div relatively to width of browser window
body: <p>How can I set the <code>width</code> property of a <code>div</code> so that it is always a percentage of the browser window's width?</p>
  
  <p>For example, </p>
  
  <ul>
  <li>when the width of the browser window is 1920px, the <code>div</code>'s width is 1536px (80%)</li>
  <li>when the width of the browser window is 1600px, the <code>div</code>'s width is 1280px (80%)</li>
  </ul>
  
  <p>and so forth?</p>