<!DOCTYPE html>
<html>
<head>
<style>
.box {
width: 300px;
height: 200px;
border: 1px solid #ccc;
border-radius: 7px / 7px;
padding: 20px;
text-align: center;
position: absolute;
left: 50px;
top: 50px;
}
</style>
</head>
<body>
<div class="box">
<h1>Hello, world!</h1>
<p>This is a box with rounded corners.</p>
</div>
</body>
</html>