Please read the message 100% clearly as it states EXACTLY what your problem is. Facebook also does this.
You created your twitter application for "
www.k-linkmania.com/" you then attempted to login from "k-linkmania.com/". They are NOT the same. You need to edit your Twitter application, navigate to the @Anywhere settings and add "k-linkmania.com/" as an authorized URL. You could also from your hosting panel (if they allow redirects) redirect from the non-www to the www version of your site.