<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
<style type="text/css">
*{
margin: 0;
padding: 0;
}
html,body{
width: 100%;
height: 100%;
}
.c1{
width: 90%;
height: 90%;
}
</style>
</head>
<body>
<div class="c1"></div>
</body>
</html>