Wordpress adding "404.html" at the end of my URLs?

# BEGIN WordPress
<IfModule mod_rewrite.c>
 RewriteEngine On
 RewriteRule ^(wp-admin)($|/) - [L] # You don't want to mess with WordPress
 RewriteCond %{REQUEST_FILENAME} !-d
 RewriteCond %{REQUEST_FILENAME}\404.html-f
 RewriteRule .* $0.php

 # browser requests PHP
 RewriteCond %{THE_REQUEST} ^[A-Z]{3,9}\ /([^\ ]+)\404.html
 RewriteRule ^/?(.*)\404.html$ /$1 [L,R=301]

 # check to see if the request is for a PHP file:
 RewriteCond %{REQUEST_FILENAME}\404.html -f
 RewriteRule ^/?(.*)$ /$1404.html [L]
</IfModule>
# END WordPress