What is a CardDAV account password?

CardDAV is simply a method to save contact data on a server so that you can 'subscribe' to that service & have the same data on different devices. CalDAV is used for calendars.

It could be an error with iCloud or possibly any other service - it is not just a Yahoo feature, it is a standard for sharing this type of info.

Next time the error appears take a screen shot of the dialog – press cmd+shift+4 then drag the crosshair over the dialog - it will grab that area of the screen. Post the image from the Desktop here via the camera icon on the form.

You can also examine Contacts (or Address Book). Look in the Preferences to see what accounts are setup.

Frankly these dialogs can occasionally appear if you have flaky internet or if the service is not very reliable, but you should try to confirm what service it is from.

P.S. Are you using OS X 10.7? Apple menu > About this Mac will state the version.

It would sound like one or more of your existing contacts would have been placed there via a CardDAV server.

Do you have an older contact that may have been synced that way?

No other logical reason for that prompt.

Look at each contact. This would be an older one. See if the data fields are different. Maybe the prompt for an update will come up when you look at it.

Great,

I'm glad it helped.