Bad value X for attribute “colspan” on element “td”: Expected a digit but saw Y instead.

The colspan attribute of a <td> takes digits only, so a single space after the number, as in colspan="2 ", makes the value invalid.

The space usually comes from a template. In <td colspan="{{ span }} "> or <td colspan="<?php echo $span; ?> ">, the space before the closing quote ends up in the attribute, right after the number. A helper that pads numbers to a fixed width has the same effect. A space before the number (" 2") or a line break inside the quotes gets the same error. The character after "saw" is the first one that isn't a digit: a blank here, p in 2px, % in 50%. A value with markup in it, like 2><span class=, means a closing quote is missing.

The HTML standard requires colspan to be a valid non-negative integer greater than zero and no larger than 1000, which is one or more digits with nothing around them. Browsers skip leading spaces, read the digits and ignore the rest, so "2 " still spans two columns. The validator's table check counts a cell with a trailing space as one column, though, so a "table row was N columns wide" warning often appears alongside this error.

Fix the template so the closing quote comes right after the number, or trim the value before printing it.

Invalid example

<table>
  <tr>
    <th>Item</th>
    <th>Qty</th>
    <th>Price</th>
  </tr>
  <tr>
    <td>Notebook</td>
    <td>2</td>
    <td>$8</td>
  </tr>
  <tr>
    <td colspan="2 ">Total</td>
    <td>$8</td>
  </tr>
</table>

Valid example

<table>
  <tr>
    <th>Item</th>
    <th>Qty</th>
    <th>Price</th>
  </tr>
  <tr>
    <td>Notebook</td>
    <td>2</td>
    <td>$8</td>
  </tr>
  <tr>
    <td colspan="2">Total</td>
    <td>$8</td>
  </tr>
</table>

Learn more:

MDN Reference

MDN Web Docs: The table data cell element

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WHATWG Spec

HTML Standard: Tabular data

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WHATWG Spec

HTML Standard: Common microsyntaxes

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