table having header cell spanning two rows are also very often seen.

HTML

<table>
			<thead>
				<tr>
					<th colspan="2">Major 1</th>
					<th colspan="2">Major 2</th>
					<th rowspan="2">col 5</th>
				</tr>
				<tr>
					<th>col1</th>
					<th>col2</th>
					<th>col3</th>
					<th>col4</th>
				</tr>
			</thead>
			<tbody>
				<tr>
					<td>data1</td>
					<td>data2</td>
					<td>data3</td>
					<td>data4</td>
					<td>data5</td>
				</tr>
			</tbody>
		</table>

CSS

table tr th, table tr td {
	border: 1px solid blue;
  }