# CodeIgniter User Guide Version 1.7.3

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# Upgrading from 1.7.1 to 1.7.2

Before performing an update you should take your site offline by replacing the index.php file with a static one.

## Step 1: Update your CodeIgniter files

Replace these files and directories in your "system" folder with the new versions:

- system/codeigniter
- system/database
- system/helpers
- system/language
- system/libraries

Note: If you have any custom developed files in these folders please make copies of them first.

## Step 2: Remove header() from 404 error template

If you are using header() in your 404 error template, such as the case with the default `error_404.php` template shown below, remove that line of code.

`<?php header("HTTP/1.1 404 Not Found"); ?>`

404 status headers are now properly handled in the show_404() method itself.

## Step 2: Update your user guide

Please replace your local copy of the user guide with the new version, including the image files.