title: "float: right;" vs. "float: left; margin-left: Ypx" for a 2 column layout, what is best practice?
body: <p>I am creating a 2 columns layout and I was wondering if there is a practical difference between using, for the second column, "float: right;" vs. "float: left; margin-left: Ypx".</p>
  
  <pre><code>&lt;html&gt;
  &lt;head&gt;
  &lt;style type="text/css"&gt;
  * {
       margin: 0;
       padding: 0;
  }
  
  #main {
      width: 900px;
      margin: 0 auto;
  }
  
  #right {
      float: left;
      width: 600px;
  }
  
  #left {
      float: left;
      width: 280px;
      margin-left: 20px;
  }
  &lt;/style&gt;
  &lt;/head&gt;
  &lt;body&gt;
  &lt;div id="main"&gt;
    &lt;div id="left"&gt;Content of the left column
    &lt;/div&gt;
    &lt;div id="right"&gt;Content of the right one
    &lt;/div&gt;
  &lt;/div&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>