<!DOCTYPE html>
<html>
<head>
<style>
table, th, td {
border: 1px solid black;
}
</style>
</head>
<body>
<p><b>Note:</b> The dialog tag is currently only supported in Chrome version 37+, Safari 6+ and Opera 24+.</p>
<table>
<tr>
<th>January <dialog open>This is an open dialog window</dialog></th>
<th>February</th>
<th>March</th>
</tr>
<tr>
<td>31</td>
<td>28</td>
<td>31</td>
</tr>
</table>
</body>
</html>