HTML <fieldset> name Attribute

<form action="/action_page.php" method="get">
  <fieldset name="personalia">
    <label for="fname">First name:</label>
    <input type="text" id="fname" name="fname">
  </fieldset>
  <br>
  <button type="button"
  onclick="form.personalia.style.backgroundColor='yellow'">
  Change background color of fieldset</button>
  <input type="submit">
</form>