Follow the following way to fix this error. (assuming codeigniter 2.1.x)
In Codeigniter application/config/config.php file. Go to the line 129
$config['permitted_uri_chars'] = 'a-z 0-9~%.:_-';(As a security measure you are STRONGLY encouraged to restrict URLs to as few characters as possible.By default only these are allowed: a-z 0-9~%.:_-) change this code by
If you want to allow the comma(,) in your url
$config['permitted_uri_chars'] = 'a-z 0-9~%.:_,\-';Leave blank to allow all characters -- but only if you are insane.
After changes the code, save the file and refresh your browser.
DO NOT CHANGE THIS UNLESS YOU FULLY UNDERSTAND THE REPERCUSSIONS!!