Yahoo sites, the Time Warner network and Google were the top-ranked Web properties in May, according to the comScore Media Metrix monthly analysis of US consumer activity at top online properties, reports MarketingCharts.

Meanwhile, Advertising.com reached 87 percent of Americans online in May, keeping it atop comScore's Ad Focus Ranking.

Amazon sites as well as the Ask network gained one position within the Top10, each attracting more than 50 million visitors in May.

ARTISTdirect Network, a group of sites featuring multimedia music content, enjoyed a 13 percent increase in visitors and gained six spots in the rankings, while Yellowpages.com network rose 11 percent to secure the number 33 spot.

Photobucket.com LLC moved up four positions to number 29, drawing more than 21 million visitors.

Within the top 10 of the Top 50 Ad Focus Ranking, Yahoo inched up to number two, claiming a space behind Advertising.com, and Blue Lithium moved up two positions from number eight.

Centro entered the ranking at number 20, reaching 42 percent of the U.S. online population, while Undertone Networks enjoyed a nine-spot jump to number 29, more than doubling its reach.

Overall, May 2007 traffic increased to movie-related sites as the summer movie season kicked off, political sites with the presidential debates fueling interest, and e-commerce sites as consumers shopped for and purchased Mother's Day gifts.

MarketingCharts provides comScore data on those categories and more.