title: Make content at the right most in a div tag
body: <p>I have some html snippet</p>
  
  <pre><code>&lt;div id="title"&gt;This is title&lt;span id="close"&gt;X&lt;span&gt;&lt;div&gt; 
  </code></pre>
  
  <p>The width of this div is dynamical, maybe 300 600 or 800 px. I want the "X" at the right most of the div at the same line. So write a css like below:</p>
  
  <pre><code>#close
  {
     margin-right:10px;
  }
  </code></pre>
  
  <p>But it does not work. If I want to implement it, what should I config?</p>
  
  <p>Best Regards,</p>