In a fast-moving Web 2.0 world, this is how you catch lightning in a bottle: See the opportunity. Make it happen. A new generation of companies has taken the place of the startups wiped out by the dot-com crash. Armed with real business plans, they are capitalizing on trends from the increasing popularity of multimedia online to the proliferation of broadband connections. The upshot is a mushrooming digital economy in competition with traditional media along with a new set of rules for CEOs. In addition to Web sites, the Internet economy features an expanding ecosystem of support companies building infrastructure, pushing content to customers and helping with marketing and measurement in the new environment. For their part, Internet CEOs face the challenge of making money from a medium that many of its users view as ubiquitous and free. A fluid business environment without safety nets waits.