mod_rewrite - some requests being rewritten should produce a 404 but don't

I've been working on creating seo friendly urls for my site and have done this successfully with the 开发者_运维百科following rules:

RewriteEngine on
RewriteBase /

#redirect non www to www
RewriteCond %{HTTP_HOST} ^example.co.uk [NC]
RewriteRule ^(.*)$ http://www.example.co.uk/$1 [L,R=301]

# Redirect any request with page=var to /var/ format
RewriteCond %{QUERY_STRING} ^page=(.+[^/])$ [NC]
RewriteRule ^index\.cfm$ http://%{HTTP_HOST}/%1/? [R=301,L,NC]

# If not an existing file or directory rewrite any request
# to page var.
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.+[^/])/$ index.cfm?page=$1 [QSA,L]

My problem is that because of the last rule (I think), any root dir request is made into a friendly url such as /pagethatdoesntpointanywhere/ whether it points anywhere or not. Now I'd be happy with a 404 but it's not doing that it's just displaying the homepage.

I've also tried adding a blanket 404 rule:

# 404 files that don't exist
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule .+ /notfound.html [R=404,L,NC]

But that makes all of the friendly urls 404s as well.

Could someone explain where I am going wrong here please?

1. Use ErrorDocument 404 /notfound.cfm to display not found error page when Apache cannot find the file (replace notfound.cfm by your file).

2. In index.cfm, if value of page parameter is unknown (e.g. pagethatdoesntpointanywhere), display 404 error page (use the same/similar code as notfound.cfm). It is the right place to do considering your rewrite rules and the fact that you checking which page to display here anyway. Lots of products/frameworks work in similar fashion (for example: WordPress).

Use both #1 and #2. Number #2 will work for 1-folder deep URLs (e.g /meow/) while #1 will catch any other URLs (e.f. /meow/kitten/ or /meow/wuf/oink.css).