title: Why is one span thicker than the other although they have the exact same height?
body: <p>I have the following very simple HTML-structure:</p>
  <p>2 <code>span</code> inside one parent <code>div</code>. Both <code>span</code> have the exact same height of <code>1px</code>. But still one of them looks thicker than the other one. I assume it has to do something with the margin but I don't know what and why.</p>
  <h2>EDIT:</h2>
  <p>Since a lot of people commented that they couldn't see the problem. Here is a screenshot of my view:</p>
  <p><a href="https://i.stack.imgur.com/6Xllp.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/6Xllp.png" alt="enter image description here" /></a></p>
  <p>It might be a screen-size- or zooming-problem?</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>body {
    margin: 0;
    padding: 0;
  }
  
  .parent {
    display: block;
    background: lightgray;
    width: 50px;
  }
  
  span {
    display: block;
    height: 1px;
    margin-bottom: 40px;
    width: 50%;
    background: black;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
    &lt;body&gt;
     &lt;div class="parent"&gt;
      &lt;span&gt;&lt;/span&gt;    
      &lt;span&gt;&lt;/span&gt;
     &lt;/div&gt;
    &lt;/body&gt;
  &lt;/html&gt;</code></pre>
  </div>
  </div>
  </p>