No private data at all is stored on the Counterwallet servers.
EDIT: Corrected to encouraging everyone to secure your passphrase. Phantom is correct. All crypto and security takes place in the browser not on the server.
If there is no private keys on the server?
Please tell me this!!
Counterwallet uses deterministic seed just like electrum, it doesn't store your password on the server in any way. So the only way you would have a chance to lose money is if your personal machine was compromised or you handed that info over to someone.
Please correct me if I'm wrong, but didn't Counterwallet get hacked and a few bitcoins got stolen?
How this could happen is what I wounder, since you say it's not possible.