Yahoo has topped ComScore's list of the top 50 web properties in July 2013, outpacing Google for the first time since May 2011. The ranking is based on unique visitors from the US, and does not include traffic from the company's most recent acquisition, the 133 million-blog strong Tumblr network, or traffic from mobile devices. And while Yahoo has been on a buying spree, its other recent acquisitions did not have significant web traffic of their own.

That means Yahoo has upped its traffic to existing properties, although it's hard to know which. Popular Yahoo sites include Flickr, Yahoo News, Yahoo Finance, and yes, Yahoo Answers. In May, Yahoo redesigned Flickr and added new features, so the photo-sharing network may be responsible for the bump. However, it's hard to decisively say that from the data provided.

ComScore's recent report shows Yahoo sites with a 2 percent lead over Google sites, which include Blogger and Picasa. That's a small sliver, especially given how much ComScore's traffic numbers vary month-to-month. Still, the news is a feather in CEO Marissa Mayer's cap after just over a year on the job. There were dire reports of Yahoo's declining traffic as recently as January, when Flickr was the only bright spot in what appeared to be a dying empire.

The company must keep up the traffic gains in order to prove that it's really growing. "Given how close Yahoo Sites and Google have been in recent months it can likely just be normal seasonal / month-to-month fluctuations," ComScore told MarketingLand.