Cells In A Element That Use The Headers Attribute Must Only ...
 Element That Use The Headers Attribute Must Only ...

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To fix the problem, ensure that each cell in a table using headers refers to another cell in the same table by creating a scope attribute value on each th element within tr elements. This rule checks that references to header columns and rows connect to specific td elements.

The scope attribute tells the browser and screen reader that everything under the column is related to the header at the top, and everything to the right of the row header is related to that header.

Applying the scope attribute to our table the markup now looks like this:

Example

<table> <caption><strong>Greensprings Running Club Personal Bests</strong></caption> <thead> <tr> <th scope="col">Name</th> <th scope="col">1 mile</th> <th scope="col">5 km</th> <th scope="col">10 km</th> </tr> </thead> <tbody> <tr> <th scope="row">Mary</th> <td>8:32</td> <td>28:04</td> <td>1:01:16</td> </tr> <tr> <th scope="row">Betsy</th> <td>7:43</td> <td>26:47</td> <td>55:38</td> </tr> <tr> <th scope="row">Matt</th> <td>7:55</td> <td>27:29</td> <td>57:04</td> </tr> <tr> <th scope="row">Todd</th> <td>7:01</td> <td>24:21</td> <td>50:35</td> </tr> </tbody> </table>

See Using id and headers attributes to associate data cells with header cells in data tables for a specific example connecting data cells to one ore more header cell within a data table.

Note that the top headers for Name, 1 mile, 5 km and 10 km are all marked up with th elements, as are the row headers for Mary, Betsy, Matt and Todd. Each of these header cell have also been given the scope attribute values of col or row depending on whether they are column or row header cells.

One more method to associating header cells with data cells uses the colgroup and rowgroup values of the scope attribute. This markup technique is use to indicate headers spanning multiple columns or rows. Consider the following table from Mozilla's Learn HTML Developer Docs:

Items Sold August 2016
Clothes Accessories
Trousers Skirts Dresses Bracelets Rings
Belgium Antwerp 56 22 43 72 23
Gent 46 18 50 61 15
Brussels 51 27 38 69 28
The Netherlands Amsterdam 89 34 69 85 38
Utrecht 80 12 43 36 19

Example including scope="colgroup" and scope="rowgroup" values on th elements

<table> <caption>Items Sold August 2016</caption> <tbody> <tr> <td></td> <td></td> <th colspan="3" scope="colgroup">Clothes</th> <th colspan="2" scope="colgroup">Accessories</th> </tr> <tr> <td></td> <td></td> <th scope="col">Trousers</th> <th scope="col">Skirts</th> <th scope="col">Dresses</th> <th scope="col">Bracelets</th> <th scope="col">Rings</th> </tr> <tr> <th rowspan="3" scope="rowgroup">Belgium</th> <th scope="row">Antwerp</th> <td>56</td> <td>22</td> <td>43</td> <td>72</td> <td>23</td> </tr> <tr> <th scope="row">Gent</th> <td>46</td> <td>18</td> <td>50</td> <td>61</td> <td>15</td> </tr> <tr> <th scope="row">Brussels</th> <td>51</td> <td>27</td> <td>38</td> <td>69</td> <td>28</td> </tr> <tr> <th rowspan="2" scope="rowgroup">The Netherlands</th> <th scope="row">Amsterdam</th> <td>89</td> <td>34</td> <td>69</td> <td>85</td> <td>38</td> </tr> <tr> <th scope="row">Utrecht</th> <td>80</td> <td>12</td> <td>43</td> <td>36</td> <td>19</td> </tr> </tbody> </table>