title: Fix Google PageSpeed's "Serve scaled images" for responsive layout
body: <p>My layout is responsive so I need to have scaled images put into the template, e.g. when using mobile devices, the <code>span3</code> of <code>Boostrap</code> might occupy  a full row so the width will be increased.</p>
  
  <p>But in the Google PageSpeed it is marked as an issue.</p>
  
  <p>Are there any workaround or a better way to handle this?</p>