[caption id="attachment_11781" align="aligncenter" width="618"] A familiar sight to many people, apparently.[/caption] Yahoo had the most-visited Web properties in the U.S. last month, according to research firm comScore. If Yahoo manages to maintain (or even widen) that lead over its biggest rivals, it could validate the corporate strategy pursued by CEO Marissa Mayer, who is seeking to blow the dust off her company’s aging properties. As part of that strategy, she’s engaged in an aggressive flurry of acquisitions, including Tumblr and Summly. Tumblr isn’t included in Yahoo’s tally, suggested a comScore statement sent to Marketing Land: “Seems there are other factors at play, and given how close Yahoo Sites and Google have been in recent months it can likely just be normal season/month-to-month fluctuations.” Marketing Land believes this is the first time since 2008 that Yahoo’s owned that top spot in the Web-audience rankings. Yahoo’s victory also comes with one very important caveat: according to AllThingsD, comScore’s numbers don’t include mobile, which is the increasing focus of Google, Facebook, and pretty much every other serious Web competitor out there. Facebook has devoted considerable resources to mobile, for example, in an effort to expand its presence into new markets—particularly in developing countries, where a phone is often someone’s first computing device. Mobile also presents an enticing source of ad revenue at a time when all tech companies are aggressively competing for eyeballs and profits. Mobile apps such as Facebook Home and Google Now are becoming gateways through which people access their Web content and services while on the go. In other words, while Yahoo’s victory is certainly worth some buzz, the company’s fight to revitalize its brand is taking place in multiple dimensions. If Yahoo engages in a solid mobile strategy, and figures out a way to unite its disparate properties (including new ones such as Tumblr) into an engaging whole, it could succeed in taking that battle to its competitors. But if it can’t triumph on those fronts, Yahoo’s current victory will be no more than a blip.   Image: Yahoo