How do I delete duplicate contacts in iCloud? All contacts have a duplicate.

I have a rather large contact file organized in groups. When I open Contacts in iCloud.com each contact appears twice. How do I easily delete the duplicates and how can I avoid getting duplicates the next time I sync? Should I delete all my contacts in iCloud Contacts? How? My iPhone shows the same contacts but no duplicates. I'm nervous that the next time I sync I will get NO contacts on all my devices. I do have original contact list on my PC in 2003 Outlook.