Vertical align not working on inline-block
<p>I was told that:</p>

<blockquote>
  <p>Vertical align only works for inline,inline-blocks,images,and table
  elements. <br>It has to be applied on the child element, as oppose to the
  parent element, unlike text-align.</p>
</blockquote>

<p>However, when I tried to set vertical align middle on an inline-block element, it didn't work. Why?</p>

<p><div class="snippet" data-lang="js" data-hide="false">
<div class="snippet-code">
<pre class="snippet-code-css lang-css prettyprint-override"><code>#wrapper {
border: 1px solid black;
width: 500px;
height: 500px;
}
#content {
border: 1px solid black;
display: inline-block;
vertical-align: middle;
}</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div id = 'wrapper'&gt;
&lt;div id = 'content'&gt; content &lt;/div&gt;
&lt;/div&gt;</code></pre>
</div>
</div>
</p>