HTML Checking for Large Sites

Rocket Validator integrates the W3C Validator HTML checker into an automated web crawler.

The “label” element may contain at most one “button”, “input”, “meter”, “output”, “progress”, “select”, or “textarea” descendant.

The label element may contain only one labelable descendant.

For example:

<label for="age">
  Age
  <select id="age">
    <option>young</option>
    <option>old</option>
  </select>
</label>

Learn more:

Related W3C validator issues