I want to have directories such as www.mydomain.com/user1 actually access www.mydomain.com/users/user1.
How can I do this in the .htaccess file without affecting the redirection of other files and directroies on the server?
Many thanks.

RewriteEngine On
# if requested filename is not an existing file
RewriteCond %{REQUEST_FILENAME} !-f
# ... and not an existing directory
RewriteCond %{REQUEST_FILENAME} !-d
# rewrite any path that doesn't contain a dot to /users folder
RewriteRule ^([^.]+)$ http://www.mydomain.com/users/$1 [L]