title: Setting element height in responsive layout?
body: <p>Generally, what markup and CSS will create an element with a percentage-based height in a responsive design? <a href="https://stackoverflow.com/questions/8740779/how-to-build-a-2-column-fixed-fluid-layout-with-twitter-bootstrap">How to build a 2 Column (Fixed - Fluid) Layout with Twitter Bootstrap?</a> shows how to create two 100% height columns, but this breaks for heights &lt; 100%.</p>
  
  <p>Specifically, I have a sidebar div with a list of items, which may be short (empty) or long (<code>overflow: auto</code>). But because no parent elements have a fixed height, <code>height: 20%;</code> does not work. How can I give the sidebar a fluid height while maintaining a responsive design?</p>