How/Why does a "/" in the URL affect umlauts?

[TLMD]

If I am linking to a page that does not exist, vB5 displays an error message ("Wrong URL. If this error..."). I have translated this message ("Ungültige URL. Wenn dieser Fehler..."). Now here is what I do not understand:

If the link has no "/" at the end – www.example.com/a-page-that-does-not-exist –, then the message shows up correctly ("Ungültige URL").

If the link, for whatever reason, has a "/" at the end – www.example.com/a-page-that-does-not-exist/ –, then the message has some issues ("Ungültige URL").

1. Why does that happen? Where is the difference between an URL with and without a "/"? (I thought there was none.)
2. How can I force the message to display correctly?
3. Is there a way to make the "/" disappear automatically, if someone enters an URL with a "/" at the end? This does already happen, if I enter an URL to an existing page.

[Zachery]

I'll see if I can't get someone to look into the issue, or at least give you an explanation.