://www.stevesouders.com/blog/2009/06/18/simplifying-css-selectors/">performance reasons</a>.</p>

<pre><code class="language-css bad">/* Not recommended */
ul.example {}
div.error {}
</code></pre>

<pre><code class="language-css good">/* Recommended */
.example {}
.error {}
</code></pre>

<h4 id="ID_Selectors" class="numbered">ID Selectors</h4>

<p>Avoid ID selectors.</p>

<p>ID attributes are expected to be unique across an entire page, which is
difficult to guarantee when a page contains many components w