When you hit the “Original” radio button at the top, you see English, with German in the yellow hover box.
If you visit the original English site, you don’t see a translation, not even on hover.
You switch to English by replacing /de-de/ in the URL with /en-us/. As in
German (translation or original with translation on hover):
http://msdn.microsoft.com/de-de/library/system.diagnostics.contracts.contractargumentvalidatorattribute(v=vs.110).aspx
English only (no translation):
http://msdn.microsoft.com/en-us/library/system.diagnostics.contracts.contractargumentvalidatorattribute(v=vs.110).aspx