title: auto expand div height
body: <p><a href="https://i.stack.imgur.com/FSbRK.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/FSbRK.jpg" alt="alt text"></a>
  </p>
  
  <pre><code>&lt;html&gt;&lt;head&gt;&lt;title&gt;Test&lt;/title&gt;
  &lt;style&gt;
  .main{width:600px;border:1px solid red; }
  .main .left{background:lightblue; width:100px;clear:both; float:left;}
  .main .right{margin-left:100px;background:lightyellow; }
  &lt;/style&gt;
      &lt;/head&gt;&lt;body&gt;
  &lt;div class="main"&gt;
      &lt;div class="left"&gt;
      title
      &lt;/div&gt;
      &lt;div class="right"&gt;
          &lt;div id="item"&gt;item&lt;/div&gt;
          &lt;div id="item"&gt;item&lt;/div&gt;
          &lt;div id="item"&gt;item&lt;/div&gt;
          &lt;div id="item"&gt;item&lt;/div&gt;
          &lt;div id="item"&gt;item&lt;/div&gt;
          &lt;div id="item"&gt;item&lt;/div&gt;
          &lt;div id="item"&gt;item&lt;/div&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  &lt;/body&gt;&lt;/html&gt;
  </code></pre>
  
  <p>How to change the CSS to make the page display like the dialog shows?</p>
  
  <p>PS,I think it's a way that to make the "left" div's height auto expand when the height of the "right" div or parent div expand, but I don't know how.</p>