Skype identity of developer cannot be confirmed error

The easy solution to this error message is to use Quarantino (free download) to remove Skype.app from Quarantine.

1. Open the Skype DMG.
2. Copy Skype.app to the Desktop.
3. Launch Quarantino.app and from the File menu, choose Open...
4. Choose Skype.app
5. Ensure that the publisher is correct and Apple verified (look for Apple logo)
6. Choose the 'Remove from Quarantine' button.