There appears to be an issue. The styles assigned to the second element should change when hovering over it, only if the third element has the class .active.
CSS:
li:nth-child(3).active ~ li:nth-child(2):hover
HTML:
<ul>
<li>
<h1 id="logo">Logo</h1>
</li>
<li>
<a href="#">Products</a>
</li>
<li class="active">
<a href="#">Parts</a>
</li>
<li>
<a href="#">Resources</a>
</li>
</ul>