• by Mark Walsh  @markfwal, July 22, 2011

Yahoo yielded the No. 1 spot to Google in June for the first time in eight months, according to comScore's latest ranking of the top 50 Web properties. The search giant drew 182.5 million unique visitors last month, compared to 178.3 million for Yahoo, whose traffic slipped about 6% from May. Google's audience increased slightly from 180 million.

The Web rivals have been in a virtual dead heat for much of the year in traffic, but Google has not held the top slot outright since last October, when it edged out Yahoo 180.6 million to 179.6 million in monthly visitors. The comScore report comes on the heels of Yahoo reporting second-quarter results that fell below Wall Street's expectations, due to softening display ad sales.

Yahoo's June swoon reflects a fall-off after traffic spikes in April and May, likely as a result of big stories, including the royal wedding and the killing of Osama bin Laden. These are the kind of news events that Yahoo has long relied on to boost monthly traffic and user engagement. In June, the Web portal's audience dropped back to the level where it has been for most of the year: around 180 million.

Whether early interest in Google+ had anything to do with Google's uptick in June is unclear, especially since the much-heralded new social-networking service did not launch in beta until the very end of the month. But comScore separately  reported Friday that Google+ had gotten often to a fast start, attracting 20 million visitors worldwide in 21 days.

The rapid embrace of the new social network to date suggests Google's hold on the No. 1 audience spot may last beyond June.

Among other top sites, Microsoft, Facebook and AOL again rounded out the top five -- with traffic of 179.7 million, 157.2 million, and 115 million, respectively.

The top-gaining Web properties in June included ABC Family, American Express, Dish Network Corporation, the Mozilla Organization and ImageShack. Just behind was Groupon, which replaced group-buying rival LivingSocial among the top 10 fastest-growing sites. Groupon's monthly audience increased 20% to 14.5 million.