The simplest way to create custom error pages is to edit the files at /application/views/errors/html/error_*.php such as error_404.php (for 404s), error_db.php (for database errors) and error_general.php (for most other errors).

As these pages are within your application directory, you are free to customise them to your needs.

If your normal view template looks something like this:

<?php $this->load->view('includes/header'); ?>
<?php $this->load->view('includes/footer'); ?>

You can adapt this in your /application/views/errors/html/error_*.php files like so:

  $page_title = $heading;
  include VIEWPATH.'includes'.DIRECTORY_SEPARATOR.'header.php';
<div class="well">
  <h1><?php echo $heading; ?></h1>
  <?php echo $message; ?>
<?php include VIEWPATH.'includes'.DIRECTORY_SEPARATOR.'footer.php'; ?>

Notice that we’re no longer using views, but instead including the view files for the header & footer.

Another thing to note:

In the header view, I’m passing a $data object which includes $data['page_title']. As the error pages don’t use views, you have to add any variables that you’d normally pass into the view, hence the presence of $page_title.

Why use this approach?

The big advantage of this approach over the various other techniques is the simplicity. You simply override the existing views in /application/views/errors/html/error_*.php and use the existing logic to display the various error pages.