There are no rules here, only conventions. In my opinion, a copyright year in the past makes it look like you don't know what you're doing. If you feel the need to tout your long history, then put the start and current year, like 2011-2013. Otherwise, follow convention and make sure it always reads the current year.
That work will (hopefully) enter the public domain one day. By forward-dating the copyright notice, you are attempting to fraudulently extend your limited monopoly.
As far as I know, this is untested in court for online documents. There is an argument that says that each HTTP request is an act of publication, thus updating the copyright date to that point in time. It's not a view I subscribe to personally.
Copyright is dated to first publication. Re-publication is irrelevant. Disney doesn't get to extend the copyright on Mickey Mouse by re-issuing steamboat Willy. They have to bribe politician for that.
