Welcome to the Weekend Web

There's only one Web. At least that's been the standard response in many tech circles to the emergence of the wireless Web. The point? No matter how you get online, be it by PC or smartphone, you'll still do the same things on the Web, using roughly the same sites and services. Really?

David Witkowski missed that memo. Witkowski, an executive at a Silicon Valley startup, behaves very differently when he uses the Web on a PC compared with when he's surfing via cell phone. From the office computer, "I pretty much live on Google," Witkowski says. But from his Research In Motion (RIMM) BlackBerry, the amateur radio enthusiast spends a lot of time searching for gadgets for sale on Craigslist, especially when he travels and on weekends. He also checks local weather forecasts and airline schedules.

Welcome to the weekend Web, where people are spending a bigger slice of time online via wireless devices—and using a different set of sites than during the workweek. "At Google, we see the majority of our desktop traffic [in the U.S.] during weekdays," says Matt Waddell, chief of staff for Google (GOOG) Mobile. "On mobile, the situation is completely reversed." Mobile browsing surged 89% in the past year, with mobile page views increasing by 127%, according to researcher M:Metrics. The increase reflects growing availability of all-you-can eat data plans and increasingly sophisticated handheld devices such as the Apple (AAPL) iPhone.

On Saturday, Classifieds Rule

Of course, most Web surfing still happens via PC, but M:Metrics' research shows that when it occurs by way of mobile, much of it takes place on the weekend. The number of unique visitors to the mobile Web spikes on Saturdays, according to March figures compiled by M:Metrics. The number surged to 4.17 million on Saturdays, an 8% increase from Fridays and 4% more than on the next busiest day, Monday, according to the study, which tracked behavior by 1,861 U.S. smartphone owners.

And like Witkowski, lots of U.S. cell phone users flock to a different set of sites via handheld. Many swarm Craigslist, the local classified ad site. In March, users spent more time on Craigslist than on any other site. "Very few Web sites are inherently local; ours is the exception," says Craigslist CEO Jim Buckmaster. When it comes to sites visited from a PC, Yahoo! (YHOO) properties hold the No. 1 spot, while Craigslist is way down in ninth place, according to researcher comScore Media Metrix.

Electronic commerce site eBay (EBAY) is No. 2 in time spent on mobile, while it's only No. 8 on the PC Web, according to M:Metrics and comScore. The Weather Channel gets the fourth-highest number of unique visits on the mobile Web, according to Nielsen Mobile, but it's way down the rankings at No. 26 on the PC Web, according to Amazon's (AMZN) Alexa traffic monitoring service. Map provider MapQuest, owned by AOL, is the eighth-most visited mobile site, according to Neilsen, but ranks 35 on the PC Web, according to Alexa.

"Personal Concierge"

During the week, Americans run Google and Yahoo searches at work and compose blogs on MySpace and Facebook. The PC Web's fastest-growing site categories include pharmacies, food, cosmetics, and job search, according to comScore. During weekends, we fire up our smartphones for fun. The fastest-growing mobile-Web categories relate to weather, entertainment, games, and music, according to comScore.

Where Portals and Social Networks Collide

Let’s Grab Google’s Gazillions