this document has the file name content_neg_test_2.html.en on the server side

you should see content_neg_test_2.html.en if the href was content_neg_test_2.html.en

OR

you should see content_neg_test.html if the href was content_neg_test.html

now go and change the settings of your browsers favourit language to german (de). and relaod this page ... with content_neg_test.html