@Stijn: Do you get a 404 when trying to access the products.asp URLs? Or what is the issue? Maybe you have to set the RewriteBase as well, or change the RewriteRule.. it all depends on your Site structure. Is the site running in a subfolder by any chance?

| Do you get a 404 when trying to access the products.asp URLs? Or what is the issue?

Yes, when I look for a url like this: /products.asp?productgroupid=5&language=nl I get the 404 error that I set in SilverStripe.

I don't want the error when people use that url.

| Is the site running in a subfolder by any chance?

No subdir ..

Post the contents of your .htaccess and the link to your site?

Can't post the site, but this is the content:

### SILVERSTRIPE START ###
<Files *.ss>
Order deny,allow
Deny from all
Allow from 127.0.0.1
</Files>

<IfModule mod_rewrite.c>
RewriteEngine On

RewriteCond %{REQUEST_URI} !(\.gif$)|(\.jpg$)|(\.png$)|(\.css$)|(\.js$) 

RewriteCond %{REQUEST_URI} ^(.*)$
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule .* sapphire/main.php?url=%1&%{QUERY_STRING} [L]
RewriteRule ^products.asp$ /home/nl [R=301,QSA,L]

</IfModule>


### SILVERSTRIPE END ###

In my first reply, I wrote to put the rewrite rule before the SilverStripe rewrite-rules. So here's how it should look like for your site:

### SILVERSTRIPE START ###
<Files *.ss>
Order deny,allow
Deny from all
Allow from 127.0.0.1
</Files>

<IfModule mod_rewrite.c>
RewriteEngine On

RewriteRule ^products.asp$ /home/nl [R=301,QSA,L]

RewriteCond %{REQUEST_URI} !(\.gif$)|(\.jpg$)|(\.png$)|(\.css$)|(\.js$)

RewriteCond %{REQUEST_URI} ^(.*)$
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule .* sapphire/main.php?url=%1&%{QUERY_STRING} [L]
</IfModule>
### SILVERSTRIPE END ###

Thx! Now its works! I must mis read it :$