how to use id to apply css code example

Example 1: css id

<style>
	#your_id{
		color: blue;
		font-size: 24px;
	}
</style>
<h1 id="your_id">Example text</h1>

Example 2: div id css

<p class="haut">
<a href="#haut">Haut de page</a>
</p>