title: Why does z-index not work?
body: <p>So if I understand <code>z-index</code> correctly, it would be perfect in this situation: </p>
  
  <p><img src="https://i.stack.imgur.com/UFHRb.jpg" alt="enter image description here"></p>
  
  <p>I want to place the bottom image (the tag/card) below the div above it. So you can't see the sharp edges. How do I do this?</p>
  
  <pre><code>z-index:-1 // on the image tag/card
  </code></pre>
  
  <p>or</p>
  
  <pre><code>z-index:100 // on the div above
  </code></pre>
  
  <p>doesn't work either. Neither does a combination of anything like this. How come?</p>