html table with separated column without outer border
<!DOCTYPE html>
<html lang="en">
<head>
<style>
th, td {
border: 1px solid black;
}
</style>
</head>
<body>
<table style="width:100%">
<tr>
<th>Firstname</th>
<th>Lastname</th>
<th>Age</th>
</tr>
</table>
</body>
</html>