This has been asked many, many, many times before.
This is very unlikely to ever change as the Stack Exchange network is built in the USA: the programmers, designers and owners of the SE network cannot think of any reason why voting should be anything else then anonymous. It's in their law, so just accept things the way they are as you'll never change them and do like me:
###Always leave a comment yourself when down-voting!
Eventually... when most users will comment while down-voting, we'll have a case for making voting public instead of secret... Until then: be a shining example to everyone else out there! ;-)