Modifying Rewrite Rule in .htaccess file - .htaccess

Question

In my .htaccess file this piece of code is present:
<IfModule mod_php5.c>
php_flag magic_quotes_gpc off
php_flag magic_quotes_sybase off
php_flag register_globals off
php_flag session.auto_start off
php_value mbstring.http_input pass
php_value mbstring.http_output pass
php_flag mbstring.encoding_translation off
php_value max_execution_time 200
php_value output_buffering 4096
php_flag display_errors On
php_value session.gc_maxlifetime 1000
php_value session_set_cookie_params 1000
php_value session.bug_compat_42 off
php_value session.bug_compat_warn off
php_value session.cookie_httponly true
Options FollowSymLinks
Options -Indexes
php_flag display_startup_errors off
php_flag display_errors off
php_flag html_errors off
php_flag log_errors On
</IfModule>
RewriteEngine On
RewriteCond %{REQUEST_METHOD} ^(TRACE|TRACK|OPTIONS|HEAD)
RewriteRule .* - [F]
<ifModule mod_headers.c>
Header set X-XSS-Protection "1; mode=block"
Header append X-FRAME-OPTIONS "SAMEORIGIN"
Header set X-Content-Type-Options: "nosniff”
</ifModule>
Header append X-FRAME-OPTIONS "Deny"
RequestHeader unset X-Forwarded-For
<Files phperrors.log>
Order allow,deny
Deny from all
Satisfy All
</Files>
<Files phpaccess.log>
Order allow,deny
Deny from all
Satisfy All
</Files>
<Files ~ "^\w+\.(gif|jpe?g|png|doc|pdf)$">
order deny,allow
allow from all
Satisfy All
</Files>
ErrorDocument 404 http://example.com/content/error.php
And I think the code is redirecting every unwanted/suspicious URL call to error page.
I have created a sub folder inside the domain and I want to call it like this in URL: http://example.com/sub_folder but it is redirecting me every time to error page (http://example.com/content/error.php).
How can I include the rule in the .htaccess file, that I will be able to load the sub folder's content?
Thanks