If you are seeing this, your .htaccess file is configured incorrectly or doesn't exist.
Copy and paste the code below into your .htaccess file
DirectoryIndex index.php
php_flag register_globals off
php_flag magic_quotes_gpc off
FileETag none
ServerSignature Off
Options All -Indexes
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteRule ^shorten/(.*)$ shorten.php?longurl=$1 [L]
RewriteRule ^([0-9a-zA-Z]{1,6})$ redirect.php?url=$1 [L]
</IfModule>
For detailed instructions, visit Brian Cray