'Adaptive Web site', particulary, 'personalized website', is a requisite contrivance at, for example, university course site (my case). (Note: Personalization site fails if it is at discretion of such users as don't have a compelling reason to personalize.)
"Adaptive" means "customize content and interface to each user individually". — Cf. In the case of traditional, "static" Web sites, the way to target diverse users is aiming at generalized types of user (but what follows the generarization is that each individual does not quite fit to the site).
The main technology which brings in "adaptive Web site" is server-side coding with database driven.