It's because your firefox version is old (and doesn't support websocket). The message will be more accurate in short. See 55553e49f16a4e1973079e7638c941b4b03829ec
Hello I am a Debian testing user and I use Fireefox which is named Iceweasel in Debian.
The version shipped in testing is 10.0.5 as of today.
When I try to open Kune it says that my browser is not supported.
Maybe is just because the name is different (Iceweasel instead of Firefox)? Version 10 is not so old...
Thanks
Steps to reproduce:
Open http://kune.cc with Iceweasel 10.