<!DOCTYPE html>
<html>
<head>
<style>
table, th, td {
border: 1px solid black;
border-radius: 10px;
}
</style>
</head>
<body>
<h2>Table With Rounded Borders</h2>
<p>Use the CSS border-radius property to add rounded corners to the borders.</p>
<table style="width:100%">
<tr>
<th>Firstname</th>
<th>Lastname</th>
<th>Age</th>
</tr>
<tr>
<td>Jill</td>
<td>Smith</td>
<td>50</td>
