How do I remove this part? I have created a content type, but it doesn't use the following part. I want to remove it without using CSS. how can I doit?
You can implement hook_form_alter() for your content type and then do something like this inside your implementation:

// implement hook_form_alter() for cex_3dr content type:
function cex_3dr_form_alter( &amp;$form, $form_state, $form_id ) {

  if ($form_id == 'cex_3dr_node_form')
  {    
    // get rid of form elements that may confuse end-users
    unset( $form['menu'] );              
    unset( $form['body_field']['format'] );
    unset( $form['revision_information'] );
    unset( $form['path'] );
    unset( $form['attachments'] );
    unset( $form['author'] );
    unset( $form['options'] );
    unset( $form['comment_settings'] );
    unset( $form['buttons']['preview'] );
  }
}


you can also print out the contents of the form to see what fields are there, and then you know which ones to get rid of via an 'unset()'.

BTW, this is Drupal6 logic. Haven't done D7 modules yet, so the technique may vary a bit, but the concept is 'very drupal' so I'd be surprised if it were no longer possible.