Prior to 1989 all works in the US required either a copyright notice or registration filing for copyright protection. This is no longer the case, but people still do it. Note that, if present, the date should be the date of publishing of the work in question. One might be able to argue that simply updating the page to change the copyright date without actually creating and publishing a new copyrightable work is not a valid copyright notice (but, again, this is all moot since you don't even need a copyright notice these days).