SSH login in script

I want to have a script shift some files from one part of a webserver to another, and it therefore needs to use ssh. I usually login using: ssh -l <username> and then give the password. I assume it's not possible to do this in the script, so I tried using ssh-keygen to generate a public/private keypair. I then uploaded $HOME/.ssh/identity.pub to $HOME/.ssh/authorized_keys on the webserver. I was under the impression that this would allow login without asking for the password (from the manpage: "After this, the user can log in without giving the password."). But in fact I am still asked for the passphrase. Is this because the user I am locally is different from the user I am on the webserver? Have I missed something out? TIA Kevin