6.6 billion searches were conducted by Americans online in April, up four percent from last month, according to recent search engine rankings released by comScore Networks.

Google continues to dominate online search for the ninth consecutive month, sitting comfortably in first place with 43.1 percent of the market share, a slight increase from 42.7 percent in March.

As expected Yahoo! maintains its second position in the search engine rankings with 28.0 percent followed by MSN with 12.9 percent.

Interestingly, Google held a 6 percent lead in market share ahead of Yahoo! in April 2005, but has since then extended its lead from Yahoo! in the share of searches to almost 15 percent.

News Corp’s MySpace.com has entered the rankings for the first time with 43 million searches performed. This may be a sign of things to come according to comScore, who suggest that this less significant competitor in the search engine market may eventually rise in its rankings due to the immense popularity of the site.

In terms of toolbar searches, Google and Yahoo! both continue to have a firm hold on the market share, Google accounting for 48.0 percent of total toolbar searches conducted and Yahoo! following very closely with 47.6 percent of the share. Remarkably, both Google and Yahoo! combined make up just over 95 percent of all toolbar searches conducted in the U.S.