CSS_SPECIFICITY

Run
<!DOCTYPE html>
<html>
<head>
	<title>CSS Specificity</title>
	<style>
		.head {background-color: pink;}
		h1 {background-color: red;}
	</style>
</head>
<body>
	<h1 class="head">This is a heading.</h1>
</body>
</html>