Often things go wrong when you're using Euro symbols (€) or other non-ASCII symbols in a Form, and then post the form to the web server.
This web app shows how difficult it is to get it 100% right.
Fact is that you also need to do some work on the server, you have to force the request parameters to be UTF-8 encoded, before you're parsing the form....
There are two different form test pages:
(you'll discover that it doesn't matter in what encoding the page is, try it!)