title: What does -webkit-min-device-pixel-ratio: 2 stand for?
body: <pre><code>@media only screen and (max-device-width:480px), 
  only screen and (-webkit-min-device-pixel-ratio: 2)
  { /*iphone css*/ }
  </code></pre>
  
  <p><em>max-device width</em> makes sense but <em>pixel ratio</em> doesn't make any sense to me. thanks.</p>