title: Make css nth-child() only affect visible
body: <p>Is there a way to only affect visible elements with this css?</p>
  
  <pre><code>table.grid tr.alt:nth-child(odd)
  {
      background:#ebeff4;
  }
  
  table.grid tr.alt:nth-child(even)
  {
      background:#ffffff;
  }
  </code></pre>
  
  <p>If i use a <code>$('select some tr:s').hide()</code> that hides some of the rows i get a mix of odd and even styling but all in a mixup.</p>