When I visit your web site www.debian.org (using Firefox 26), your pages are displayed in Norwegian because I am living in Norway. However, I prefer English, and I have clicked on the link for English version. Nevertheless, every time I click on a new link, it is reverted to Norwegian, instead to English.
It is frustrating to get pages in Norwegian, because I use English, although I live in Norway. Your site should "remember" what user clicked on when they clicked their preferred language.