Wrong links in WordPress?

I have a project on WordPress. I would like add an article.
In admin panel I click on Post, then Categories and add a new category called article.

Next I add a new post and edit title, body and finally check the category called article.
Now i have:

Permalink: http://mypage.org/article/test

On site also is this link, but if I open this url I have:

This entry was posted in article. Bookmark the permalink. Follow
any comments here with the RSS feed for this post. Post a comment or
leave a trackback: Trackback URL. Edit

But in this url I don’t have my article. Why? In index page I have it, but if I open an article I have this error.

What can I do?

Go to Settings, then General Settings, then enter the correct url for your WordPress Address (URL). Perhaps you need to change your Site Address too.

Source: The WordPress Codex: http://codex.wordpress.org/Settings_General_Screen

If this isn’t the case, but the category links are bad, edit the category slug. Go to Posts, then Categories, select article and edit the slug. Perhaps you had a different slug beforehand.

It’s difficult to help you. It’s a game of guessing. I will stop here.