using base_url in errors/error_404.php

[eluser]Abishek R Srikaanth[/eluser]
I would like to use the base_url helper function on the errors/error_404.php and I am having trouble using it. I have tried the following ways.

Method 1:
1. Auto Loaded the URL helper.
2. Used base_url

Got the following error message when doing Method 1
"Call to an undefined function base_url"

Method 2:

Code:

$CI = '';
$CI =& get_instance();
$CI->load->helper('url');
$CI->base_url();

Get the following error when using Method 2.
"Class 'CI_Controller' not found in /var/.......//system/core/CodeIgniter.php on line 233"

Could someone please help me on this.