title: nth-child for every two table rows
body: <p>I need to make every two rows of my table grey and I would prefer to use nth-child if possible.</p>
  
  <p>I've messed around with <a href="http://css-tricks.com/examples/nth-child-tester/" rel="noreferrer">Chris Coyier's nth-child tester</a> but still can't get it.</p>
  
  <p>I need the following formula:</p>
  
  <pre><code>1,2 - grey
  3,4 - white
  5,6 - grey
  7,8 - white
  9,10 - grey
  </code></pre>
  
  <p>and so on. I'd prefer not to put a class in the html as I'm sure that's going to be a suggestion from some. If there is a way to pull this off with nth-child, that's what I'm looking for.</p>