How can I construct a table header than spans multiple rows in HTML?

Structuring headers using thead, tbody, and th

To create a table with headers spanning multiple rows, it's crucial to employ correct semantic markup. Group the header content within the thead tag, and use tbody for the body content. Each th tag denotes a unique header cell.

<! -- "thead" for headers, "tbody" for data. Just like a werewolf movie, keep 'em separated! -->
<table border="1">
  <thead>
    <tr>
      <th rowspan="2">Main Header</th>
      <th colspan="2">Secondary Header</th>
    </tr>
    <tr>
      <th>Subheader 1</th>
      <th>Subheader 2</th>
    </tr>
  </thead>
  <tbody>
    <!-- Table body content goes here -->
  </tbody>
</table>
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This structure reinforces accessibility and allows assistive technologies like screen readers to decipher the table layout. Remember, including scope attributes in th elements clearly defines their header relationships.

Aesthetic with CSS and colgroup

Your table's visual appeal can be boosted exponentially with CSS styling. Employ the border property to achieve your desired cell-separation aesthetics. For finely detailed styling, consider the col and colgroup tags.

<! -- No epic table is complete without borders. Don't let the cells escape! -->
table { border-collapse: collapse; }
th, td { border: 1px solid #000; padding: 5px; }
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To manipulate specific columns and align them in line with your visual needs, leverage the colgroup and col properties within your table:

<! -- Just like painting a house, color each column separately for a vibrant table! -->
<table>
  <colgroup>
    <col style="background-color: #DFF0D8;"/>
    <col span="2" style="background-color: #F2DEDE;"/>
  </colgroup>
  <!-- Table headers and body -->
</table>


Tough cookie: Cross-browser compatibility

Before finalizing your layout, make sure to test it across various web browsers. Each browser might interpret the table markup distinctively, turning your table into a living Rubik's cube of colors and structures! Use JSFiddle to share your puzzle with others and solve it together.

Promoting accessibility and defining relationships

To enhance readability, use th for headers and td for data cells. Additionally, use scope to visually link headers with their respective rows or columns and meet WAI-ARIA guidelines.

For tables with complex relationships between headers, it's good to peek at the advice provided by the W3C's Web Accessibility Initiative. Not only will it improve your table's accessibility, but it'll also make your headers happy!

Troubleshooting 101

When dealing with table headers spanning multiple rows, some issues are as inevitable as sand at a beach:

1. Misaligned columns: Ensure the total cells in each row (including those declared by rowspan and colspan) match the largest row to achieve pixel-perfect alignment.
2. Inconsistent styling: Use the colgroup and col tags for uniform styling and declare a fashion statement for your columns.
3. Accessibility woes: Header cells without the scope attribute confuse screen readers more than a horror movie's plot twists. Use the scope attribute to address this.

Demos and reference links

A live JSFiddle or code sandbox brings your multi-row header table to life and gives users a sandbox to play. Including links to these treasures enhances understanding while adding a cherry on top of your solution cake.