reserved keywords for subdirectory name

[eluser]searain[/eluser]

Code:

RewriteEngine on
RewriteCond $1 !^(index\.php|images|captcha|css|js|robots\.txt)
RewriteRule ^(.*)$ /index.php/$1 [L]

OK it is the .thaccess url rewrite issue.

I guess my rewritecond for |js| also covers the name 'json'.