Table column N established by element “col” has no cells beginning in it.

This table's <col> elements declare more columns than its rows fill, so column N has no <td> or <th> starting in it.

Each <col> inside a <colgroup> adds one column to the table, or as many columns as its span attribute says. The HTML table model then requires every column to have at least one cell that begins in it. A cell that only reaches the column through colspan doesn't count: with <col span="3"> and a row of <td>Alice</td><td colspan="2">2019</td>, column 3 is still reported.

The usual cause is column markup that no longer matches the content, such as a template that always writes the same <colgroup>, or a column removed from every row but left in the <colgroup>. Rows shorter than the column markup also trigger a companion error, "A table row was 2 columns wide, which is less than the column count established using column markup (3)".

To fix it, make the column markup match the rows. Remove the extra <col> elements or lower their span, or add the missing cells if that column should hold data.

Invalid example

Three <col> elements, but every row has only two cells:

<table>
  <colgroup>
    <col class="name">
    <col class="role">
    <col class="year">
  </colgroup>
  <tr>
    <th>Name</th>
    <th>Year</th>
  </tr>
  <tr>
    <td>Alice Moreno</td>
    <td>2019</td>
  </tr>
</table>

Valid example

The <colgroup> declares the same two columns the rows use:

<table>
  <colgroup>
    <col class="name">
    <col class="year">
  </colgroup>
  <tr>
    <th>Name</th>
    <th>Year</th>
  </tr>
  <tr>
    <td>Alice Moreno</td>
    <td>2019</td>
  </tr>
</table>

Learn more:

MDN Reference

MDN Web Docs: The col element

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MDN Reference

MDN Web Docs: The colgroup element

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WHATWG Spec

HTML Living Standard: Tabular data

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