<table>
	<tr>
		<th>あああ</th>
		<th>いいい</th>
	</tr>
	<tr>
		<td>ああああああああああああああああああああああああああああああああああああああああああああああああああああああああああ</td>
		<td>いいいいいい</td>
	</tr>
</table>
* {
	box-sizing: border-box;
}
body {
	min-height: 100vh;
	margin: 0;
	padding: 10px;
	display: flex;
	justify-content: center;
	align-items: center;
}
table {
	width: 100%;
	border-collapse: collapse;
}
table th,
table td {
	padding: 10px;
	border: 1px solid #ccc;
}
table th {
	background: #f5f5f5;
}

table {
	table-layout: fixed;
}

External CSS

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External JavaScript

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