title: Warning/Error in my css file: css3 document is not a known @ directive
body: <p>I am getting this message in my CSS file while trying to use media queries.  Here is the code sample:</p>
  
  <pre><code>@document url('http://www.inserthtml.com/') 
  {   
       /* CSS goes here */ 
  
  }
  </code></pre>
  
  <p>Visual Studio 2012 underlines this in red and gives the message "css3 document is not a known @ directive". Why is this?</p>