<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
		html,body{width: 100%;height: 100%;}
	</style>
</head>

<body>
<div class="c1" style="width: 50%;height: 50%;"></div>
</body>
</html>