Pages error

The pages on my website are not visible.

Although I created them in WordPress, and they are displayed in the menu, I get the following error when clicking on them:
<Error>
Not Found

The requested URL /atelier-2/ was not found on this server.

Additionally, a 404 Not Found error was encountered while trying to use an ErrorDocument to handle the request.

Apache/2.2.25 (Unix) mod_ssl/2.2.25 OpenSSL/0.9.8k DAV/2 PHP/5.3.27 Server at http://www.monsieur-velo.be Port 80
<Error>

What could be the reason?

My guess is that I don’t have a ‘Pages’ folder on my web server. So how can I add a folder to make sure the pages are automatically stored there?

Thanks!