Visits to green and travel-related websites had the most noticeable increase in March, according to the latest comScore Media Metrix report which ranks the top 50 U.S. web properties every month.

The report, which tracks where Americans spend their time online, attributed initiatives such as Earth Hour, which looks to raise awareness of energy consumption, and the approaching spring break, for the abundant increase in both categories respectively.

Website properties in the green category drew nearly 20 million unique visitors, up 11 percent from 18 million, while the travel category grew 10 percent from 55.7 to 61.3 million visitors. Other categories that followed included online instant messengers, job search, and religion-related websites.

In terms of overall rankings, Yahoo properties ranked highest with 212 million visitors, followed by Google and Microsoft with 176 million, and Facebook with 152 million. New additions to the top 50 list included, Time Warner, and BuzzMedia.

As for ad networks, Google topped once again with a 91.7% reach to Americans, followed by Yahoo with 84.4%, AOL with 83.8%, and the social media sharing widget ShareThis with 80.9%.