Ask any Web user to recall what first lured him into cyberspace; you're not likely to hear rhapsodic descriptions of a twirling animated graphic or a thin, distorted sound clip. No, the eureka moment for most of us came when we first clicked on a link, and found ourselves jettisoned across the planet. The freedom and immediacy of that movement - shuttling from site to site across the infosphere, following trails of thought wherever they led us - was genuinely unlike anything before it. We'd seen more lively cartoon animations on Saturday-morning television; we'd heard more compelling audio piped out of our home stereos. But nothing could compare to that first link.