title: H3 is taking more space than enclosing div
body: <p>I have a web page like this.</p>
  
  <pre><code>&lt;html&gt;
  &lt;head&gt;&lt;/head&gt;
  &lt;body&gt;
      &lt;div style="background:blue"&gt;
          &lt;h3 style="background:green"&gt;Hello world.&lt;/h3&gt;
      &lt;/div&gt;
  &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>
  
  <p>When I analyze the output in chrome, it seems that the h3 tag is taking more space than the div tag. I want the div tag to completely include the h3 tag, and the background color of div to be shown in the entire area. Any idea how to do this?</p>