function mymodule_form() {
  $form['container'] = array(
    '#prefix' => '<div class="container-inline">',
    '#suffix' => '</div>',
  );
 
  $form['container']['email'] = array(
    '#title' => 'E-mail',
    '#type' => 'textfield',
    '#size' => 15,
  );
 
  $form['container']['submit'] = array(
    '#type' => 'submit',
    '#value' => 'Добавить',
  );
 
  return $form;
}