From 2010-dec to 2016-dec I had a single-page website at http://xn--amt-golener-land-mlb.de/ with the following contents. In 2010, the "Amt Golßener Land" was a regional administrative entity with its own website. Sometime later this entity was subsumed into a larger one, and their domain name became a redirect to the website of the larger unit. By 2016 the old domain name had been abandoned.
What's the problem? Internet domain names are case-insensitive, and in any case-insensitive context, ß=SS=ss (and for Greek, σ=Σ=ς). Besides, in German, the spelling has been unstable and confusing for ß vs. ss, so leading people to different web sites based on this distinction is both confusing and dangerous.
Ein weiteres tolles WordPress-Blog
10. Dezember 2010
Dies ist keine Seite des “Amt Golßener Land”. Dafür gehen Sie zu http://amt-golssener-land.de/
Dies hier ist amt-golßener-land.de = xn--amt-golener-land-mlb.de
Laut IDNA2008 ist amt-golssener-land.de nicht unbedingt dasselbe wie amt-golßener-land.de und DENIC erlaubt verschiedene Betreiber für die ß und ss Varianten. Ein Internetbrowser könnte sie für amt-golßener-land.de auf diese Seite leiten. Wenn Sie sich um “phishing” sorgen, wenden Sie sich bitte an DENIC.
English
This page demonstrates that IDNA2008 does not treat amt-golssener-land.de and amt-golßener-land.de as the same domain names, and that DENIC permits different owners for these two names. An internet browser could take you to this page for amt-golßener-land.de. If you are concerned about “phishing“, you might contact DENIC.
See UTS #46: Unicode IDNA Compatibility Processing which defines International Domain Name processing that is compatible with existing practice in internet browsers.
See UTS #39: Unicode Security Mechanisms which discusses security risksrelated to character encoding, with countermeasures.