RewriteEngine On
RewriteBase /
RewriteCond %{HTTP_HOST} ^www\.(.*)$ [NC]
RewriteRule ^(.*)$ http://%1/$1 [R=301,L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^([^/]+)/$ $1.html
RewriteRule ^([^/]+)/([^/]+)/$ /$1/$2.html
RewriteRule ^([^/]+)/([^/]+)/([^/]+)/$ /$1/$2/$3.html
RewriteRule ^([^/]+)/([^/]+)/([^/]+)/([^/]+)/$ /$1/$2/$3/$4.html
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_URI} !(\.[a-zA-Z0-9]{1,5}|/)$
RewriteRule (.*)$ /$1/ [R=301,L]
ErrorDocument 404 /404.html