254988 Wordpress Error 404

I have been using my new Wordpress blog for about three weeks now I get this error message when I try to open one of my article links: Not Found The requested URL /blog/chemicals-to-avoid/alternative-to-fabric-softeners/ 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/2.0.63 (Unix) mod_ssl/2.0.63 OpenSSL/0.9.7a mod_auth_passthrough/2.1 mod_bwlimited/1.4 FrontPage/5.0.2.2635 PHP/5.2.6 Server at [login to view URL] Port 80