title: Overriding CSS properties that don't have default values
body: <p>Is it possible in CSS to override a property if that property doesn't have a default value?</p>
  
  <p>For example, say your primary stylesheet defines a border for a particular element:</p>
  
  <pre class="lang-css prettyprint-override"><code>#element {
    border: 1px solid #000;
  }
  </code></pre>
  
  <p>If you wanted to disable the border from a secondary stylesheet, you could do this:</p>
  
  <pre class="lang-css prettyprint-override"><code>#element {
    border: none;
  }
  </code></pre>
  
  <p>Assuming the secondary stylesheet was loaded after the primary one, the <code>border: none</code> rule would take precedence and remove the border.</p>
  
  <p>But what if you were trying to override a property that doesn't have a default or null value?</p>
  
  <pre class="lang-css prettyprint-override"><code>#element {
    position: absolute;
    left: 0;
  }
  </code></pre>
  
  <p>Now say, in your secondary stylesheet, you wanted to do this:</p>
  
  <pre class="lang-css prettyprint-override"><code>#element {
    right: 0;
    top: 0;
  }
  </code></pre>
  
  <p>And you didn't want any value for <code>left</code>. There's no such thing as <code>left: none;</code>, so...how do you "undeclare" the <code>left</code> property assigned in the primary stylesheet?</p>