.htaccess in Codeigniter

<IfModule mod_rewrite.c>
    Options +FollowSymLinks
    RewriteEngine On
    RewriteBase /
 
    # Removes access to the system folder by users
    RewriteCond %{REQUEST_URI} ^system.*
    RewriteRule ^(.*)$ /index.php/$1 [L]
 
    # Checks to see if the user is attempting to access a valid file
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^(.*)$ index.php/$1 [L]
 
	# Add a extension to URL
	# RewriteCond %{REQUEST_FILENAME} !-f
	# RewriteCond %{REQUEST_FILENAME} !-d
	# RewriteRule ^(.*)$ $1.php [L,QSA]
	# http://domain/about -> http://domain/about.php
 
	# Force "www." in the domain name.
	# RewriteCond %{HTTP_HOST} !^www.mydomain.com$
	# RewriteRule ^(.*)$ http://www.mydomain.com/$1 [R=301]
 
</IfModule>