A project I'm working on involves the creation of a new site that will host around 80% of the content of an old one. The content will disappear from the old site, and become solely available on the new site that we're designing, while the old site will be maintained for a period of time with that 20% of remaining content. How could we redirect our users to the new site if/when they land on the old one? The options that we have discussed are