Google

(GOOG) - Get Report

once again grew its share of the online search market, at the expense of almost everyone else, according to the latest rankings from Nielsen/NetRatings.

Yahoo!

(YHOO)

,

Microsoft

(MSFT) - Get Report

and

Time Warner's

(TWX)

AOL all lost ground in May.

Google performed more than 4 billion searches in a single month for the first time. Its share of the market jumped by 1% over the prior month to 56.3%, increasing the number of searches it performed by 260 million.

Yahoo! performed 1.5 billion searches, for 21.5% of the market, vs. a 21.9% share in April. The number of searches it performed increased somewhat.

Microsoft, which recently announced it will buy online advertising business

aQuantive

(AQNT)

to better compete against Google, saw its share of the search market drop to 8.4%, from 9% the prior month. The number of searches it performed, 605.4 million, increased slightly.

AOL lost 0.1 percentage points for a market share of 5.3%, performing 382 million searches.