Drupal Form Button + "Are you sure"-Button
Using hook_form_alter you can implement simple popups like this using #attributes.

 $form['submit']['#attributes'] =&gt; array(
  'onclick' =&gt; 'if(!confirm("Are you sure?")){return false;}',
 );


or

$form['submit']['#attributes']['onclick'] = 'if(!confirm("Are you sure?")){return false;}';