Remove text format selection from node creating page

template.php

<?php
/**
 * Remove text format selection from node creating page
 * Implements of hook_element_info_alter().
 */
function YOURTHEME_element_info_alter(&$type) {
  // Our process callback must run immediately after filter_process_format().
  $filter_process_format_location = array_search('filter_process_format', $type['text_format']['#process']);
  $replacement = array('filter_process_format', 'YOURTHEME_filter_process_format');
  array_splice($type['text_format']['#process'], $filter_process_format_location, 1, $replacement);
}
/**
 * Process callback for form elements that have a text format selector attached.
 *
 * This callback runs after filter_process_format() and performs additional
 * modifications to the form element.
 *
 * @see filter_process_format()
 */
function YOURTHEME_filter_process_format($element) {
  $element['format']['format']['#access'] = FALSE;
  $element['format']['guidelines']['#access'] = FALSE;
  $element['format']['help']['#access'] = FALSE;
  $element['format']['#type'] = 'container';
  $element['format']['#attributes']['class'][] = 'element-hidden';
  return $element;
}
?>