You may see the following error when you come to run a deployment to a particular project:
Error: The public key of your server has changed. The most likely cause of this is that you or your ISP have recently changed your server. Alternatively, it could be indicative of someone trying to hijack the connection to your server.
You can reset the public key for your server from the Edit Server Properties page. As the error explains, you can navigate to your server's properties page via the Servers & Groups area in your project, then click the "Reset Host Key" button below the main server configuration.