title: Rails Asset Pipeline: image-url not working
body: <p><strong>Context</strong></p>
  
  <p>Rails 4.</p>
  
  <p><strong>Problem</strong></p>
  
  <p>I know this has been asked many times before, but I can't get the following line of CSS to work:</p>
  
  <pre><code>background: image-url("home/smiling.jpg");
  </code></pre>
  
  <p>My file is in the right place, name is good. the line <code>background-color: red;</code> DOES work.</p>
  
  <p><strong>Attempts at a solution</strong></p>
  
  <p>SO searches.</p>
  
  <p>i've tried <code>rake assets:precompile</code>. Also <code>rake assets:clean</code></p>
  
  <p>No luck so far.</p>