Modrewrite works but error in Server Log... Why?

[StefanRSA]

I am rewriting url's in my htaccess and it is working fine

 

The pages work as it should on the site but when I inspect my server error log it gives me the following error why?

 

[Tue Mar 02 18:18:30 2010] [error] [client 165.145.140.230] File does not exist: /home/howzitc/public_html/cat, referer: http://www.mydomain.web/cat/subcat

 

In my htaccess:

RewriteRule ^([A-Za-z-]+)/([A-Za-z+-]+)$ /file.php?cat=$1&subcat=$2 [L]

 

The top of my htaccess:

IndexIgnore .htaccess */.?* *~ *# */HEADER* */README* */_vti*
##Header append X-FRAME-OPTIONS "DENY"
## Error document review
ErrorDocument 404 /index.php
AddType application/x-httpd-php .htm .xml .rss

RewriteEngine On
RewriteCond %{HTTP_USER_AGENT} libwww [NC,OR]
RewriteCond %{QUERY_STRING} ^(.*)=http [NC]
RewriteRule ^(.*)$ – [F,L]
# remove trailing slash
RewriteRule (.*)/$ /$1 [L,R=301]

RewriteRule (.*)\.xml(.*) $1.php$2 [nocase]