<!DOCTYPE html>
<html>
<head>
    <title>Xem ví dụ</title>
    <style type="text/css">
        div{
            border:10px solid black;
            padding:30px;
            width:300px;
            height:150px;
        }
    </style>
<body>
    <p>- Phần tử 1</p>
    <div style="box-sizing:content-box">
        <hr><hr><hr><hr><hr>
    </div>
    <p>- Phần tử 2</p>
    <div style="box-sizing:border-box">
        <hr><hr><hr><hr><hr>
    </div>
</body>
</html>