title: How can I make my sidebar as long as the content's height %100 on my html page ?
body: <p>My english is not so good, sorry about that.</p>
  
  <p>I'm working on a project about css and html.</p>
  
  <p>Here is my problem : I want to make my sidebar's height as long as my content page. 
  if I add something to my content page, the left nav's height should be equal the content page. </p>
  
  <p><a href="https://i.stack.imgur.com/qQ7M5.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qQ7M5.jpg" alt="enter image description here"></a></p>
  
  <pre><code>&lt;div class="container"&gt;
      &lt;div class="container-fluid"&gt;
  
          &lt;div class="leftnav"&gt;
              xxx
          &lt;/div&gt;&lt;!-- leftnav --&gt;
          &lt;div class="content"&gt;
              xx
          &lt;/div&gt;&lt;!-- content --&gt;
  
      &lt;/div&gt;&lt;!-- container-fluid --&gt;
  &lt;/div&gt; &lt;!-- container --&gt;
  
  .container{width: 1170px;margin:0px auto;}
  .container-fluid{float: left;width: 100%;}
  
  .leftnav{float: left;width: 280px;background: #fff;}
  .content{float: left;width: 890px;background: #000;}
  </code></pre>