5.2.17 to 5.3.10 hosting site upgrade breaking things (depreciation errors)

[eluser]LouRocco[/eluser]
CroNiX, I am very happy for your assistance as well!

Within /application/configh/config.php I found this line:

$config['permitted_uri_chars'] = 'a-z 0-9~%.:_\-';

What does this mean? What could I add here?
The URLs on the site appear to just be basic. Example: ".com/on_site_process"

I don't know what echo means. But I found this info at the top of the CofeIgniter.php file:

* An open source application development framework for PHP 4.3.2 or newer
*
* @package CodeIgniter
* @author ExpressionEngine Dev Team
* @copyright Copyright © 2008, EllisLab, Inc.
* @license http://ellislab.com/codeigniter/user-guide/license.html
* @LinK http://codeigniter.com
* @since Version 1.0


Any more insight would be so welcome!!

thanks, Lou