It sounds like a late-night infomercial: Go from zero to e-commerce in less than 24 hours! No HTML required! No high-paid Web design firms! Just point and click your way to an online e-commerce presence! Welcome to the wide world of browser-based build-your-own-Net-store services. Keep in mind, this approach works better for product-oriented businesses than service businesses. Essentially, you're putting together your own little Amazon.com. It's good for brick-and-mortar entrepreneurs wanting a quick online presence, but it also works for Net-only start-ups. You get a low overhead Web presence and all your services from one provider. Is a do-it-yourself Web site right for you? I visited three leaders in the arena to figure out what's alluring about them . . . and what's lacking.