Tengo debajo de .htaccess en el servidor con las reglas de página no encontradas, pero no parece funcionar. ¿Alguna idea?

RewriteEngine on
RewriteRule ^article_detail/([a-zA-Z0-9_-]+)/([0-9]+)\.html$ article_detail.php?article_det=$2
Options +FollowSymLinks
ErrorDocument 404 http://www.example.com/main/404_not_found.html


# compress text, HTML, JavaScript, CSS, and XML

<IfModule mod_ext_filter.c>
AddOutputFilterByType DEFLATE text/plain
AddOutputFilterByType DEFLATE text/html
AddOutputFilterByType DEFLATE text/xml
AddOutputFilterByType DEFLATE text/css
AddOutputFilterByType DEFLATE application/xml
AddOutputFilterByType DEFLATE application/xhtml+xml
AddOutputFilterByType DEFLATE application/rss+xml
AddOutputFilterByType DEFLATE application/javascript
AddOutputFilterByType DEFLATE application/x-javascript
# remove browser bugs
BrowserMatch ^Mozilla/4 gzip-only-text/html
BrowserMatch ^Mozilla/4\.0[678] no-gzip
BrowserMatch \bMSIE !no-gzip !gzip-only-text/html
</IfModule>