Designing Web Usability: The Practice of Simplicity by Jakob Nielsen, 1999. Every person serious about creating, designing, managing, programming or maintaining a web site should read this book. Absolutely great. Do not miss this book. Read his article on Fighting Linkrot.

As Jakob Nielson spells out in his article on Fighting Linkrot: "Any URL that has ever been exposed to the Internet should live forever: never let any URL die."

One method to help you occomplish this with your site is to use a Meta Refresh to automatically forward visitors to the new page, whenever needed. It would be preferable to avoid using them but if for some reason a page must be moved then Meta Refresh is a good alternative.

Even if you use a Meta Refresh command you should include a message with the link to the new page to the body of visitors browser window so they can click on the link if they wish (or need to if the Meta Refresh does not work for some reason).