<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
<style type="text/css">
* { margin: 0; padding: 0; }
html, body { width: 100vh; height: 100vh; }
.content { height: 100vh; width: 100vh; background: red; }
</style>
<div class="content"></div>
</body>
</html>
Простой
Средний
