Ready or not, the era of the mobile Web is upon us.

Fueled by the success of Apple Inc.’s iPhone – and new competitors like Motorola Inc.’s Droid and Palm Inc.’s Pre – the number of people accessing the Internet using a cell phone or other portable gadget is growing “explosively,” according to Mary Meeker, an influential technology analyst at Morgan Stanley.

About 57 million people have bought an iPhone or its phone-less cousin, the iPod Touch, since they went on sale in 2007. To put that number in perspective, the two pioneers of the PC-based Internet, AOL and Netscape Navigator, had eight and five times fewer users respectively after the same amount of time on the market, Meeker said.