title: CSS corner block
body: <p>I need to create a corner block with CSS &amp; html5. </p>
  
  <p>Can somebody help me? Thanks.</p>
  
  <p><strong>update:</strong>
  first of all, it should be div. I have image on my site, this is screen:
  <img src="https://i.stack.imgur.com/c2o0q.png" alt="enter image description here"></p>
  
  <p><strong>Answer:</strong></p>
  
  <pre><code>#triangle-down {
      width: 0;
      height: 0;
      border-left: 50px solid transparent;
      border-right: 50px solid transparent;
      border-top: 100px solid red;
  }
  </code></pre>