I noticed some contacts on my web-based iCloud could not be deleted.
The error message:
appeared whenever I tried to delete a contact.
In fact I want to delete all of my iCloud contacts so that I can upload a clean set.
I have tried signing out of iCloud and signing in again only to find that the old undeleteable contacts remain. If I then re-sync with my iMac address book, I get duplicate entries.
Okay. I've solved this (accidently).
By adding a new iCloud contact, the others that I couldn't delete, just disappeared! So I deleted the one I just added and found myself with a completely empty iCloud Address Book.
I simply restored my archived contacts to my iMac and checked the box to sync my Contacts in iCloud on the iMac, and hey presto the clean address book flooded into my iCloud.