title: Override one part of multiple-property css declaration
body: <p>If I have the declaration:</p>
  
  <pre><code>h1 {
    background-image: url(a.png), -webkit-linear-gradient(transparent, black), url(b.png);
  }
  </code></pre>
  
  <p>is it possible to override only one part of the multiple values, i.e. (pseudocode):</p>
  
  <pre><code>h1.foo {
    background-image: default, default, url(c.png);
  }
  </code></pre>