I'm using Pure CSS to layout a site, and I've run into an issue. If there's any whitespace between nested grid elements, it breaks the layout and pushes the last div onto the next line. I created a test website with as little in it as possible to test if it was just me, and I'm still running into the problem.
<html>
  <head>
    <link rel="stylesheet" href="http://yui.yahooapis.com/pure/0.5.0/pure-min.css">
  </head>
  <body>
    <div class="pure-g">
      <div class="pure-u-1-2">
        <div class="pure-u-1-3">
          <p>Hello world</p>
        </div>
        <div class="pure-u-1-3">
          <p>Hello</p>
        </div>
        <div class="pure-u-1-3">
          <p>Hey there</p>
        </div>
      </div>
      <div class="pure-u-1-2">
        <p>Hi :)</p>
      </div>
    </div>
  </body>
</html>
This code results in this: 
If I take the whitespace out from between the divs, as in
<div class="pure-u-1-3"><p>Hello world</p></div><div class="pure-u-1-3"><p>Hello</p></div><div class="pure-u-1-3"><p>Hey there</p></div>
it fixes itself:

This issue is occurring in both Chrome and Firefox. Is this an issue with Pure CSS, or am I doing something horribly wrong?
EDIT: I found a solution specific to YUI Pure CSS. To nest layouts, each set of columns needs to be in its own .pure-g div. I put this in more detail on the Github issue.
 
     
     
     
     
    