Websites vs. Microsites. Websites refer to the main website for a brand. Microsites (or mini-sites) refer to sites that are specific to a single message or campaign and are therefore separate from the main website. However, sometimes successful microsites become the main brand website.
A site can be an ad in itself. So can email. Try to create a webstite that makes consumers want to enter their email so they can be targeted again via subscription (until they choose to unsubscribe).