title: How to fill the entire width (React.js)?
body: <p>i'm new to React.js and the first thing i noted is that the entire width of the page is not filled. This is my JS code:</p>
  
  <pre><code>var Navbar = React.createClass({
      render: function(){
          return(
              &lt;div className="navbar"&gt; &lt;/div&gt;
          );
      }
  });
  
  ReactDOM.render( &lt;Navbar/&gt;,document.getElementById('test') );
  </code></pre>
  
  <p>And CSS:</p>
  
  <pre><code>.navbar{
      background-color: green;
      width: 100%;
      height: 3em;
  }
  </code></pre>
  
  <p>There is a 3px top, left, right unexpected margin.</p>