Include CSS or Javascript file for specific node in Drupal 6

you need to do is add a node preprocess function that adds those files for you. You can do this either in a module or in a custom theme. For a module this would be:

function mymodule_preprocess_node(&$variables) {
  $node = $variables['node'];
  if (!empty($node) && $node->nid == $the_specific_node_id) {
    drupal_add_js(drupal_get_path('module', 'mymodule') . "/file.js", "module");
    drupal_add_css(drupal_get_path('module', 'mymodule') . "/file.css", "module");
  }
}

or for a theme:

function mytheme_preprocess_node(&$variables) {
  $node = $variables['node'];
  if (!empty($node) && $node->nid == $the_specific_node_id) {
    drupal_add_js(path_to_theme() . "/file.js", "theme");
    drupal_add_css(path_to_theme(). "/file.css", "theme");
  }
} 

 when you want to insert inline code into something other than technically a node so there's no node id and no PHP input option available.