Question

While creating a (custom) content in Drupal, I have three vocabularies. But these make my create content page very heavy. I want to collapse the Vocubalary fieldset by default and want it to expand only if user chooses to.

Answer 1

If you mean that the taxonomy fieldset should be displayed as collapsed by default, you can achieve that by implementing hook_form_alter():

/**
 * Implementation of hook_form_alter().
 */
function yourModule_form_alter(&$form, &$form_state, $form_id) {
  // TODO: Adjust the form id according to your content type
  if ($form_id == 'yourContentType_node_form') {
    // Collapse 'Vocabularies' fieldset.
    $form['taxonomy']['#collapsed'] = TRUE;
  }
}