Is the mighty giant looking a little vulnerable these days? According to Reuters report last month, Google’s share of the global Web search market took a steep dive last February (even if its U.S. market share rose), Internet financial analysts revealed. ComScore research data showed that the search engine giant’s dominance of the worldwide market for Web search dipping to 62.8% in February from 63.1% the month before.

Financial analysts look at the monthly comScore search market data as an indicator on growth trends in Web search. Other monthly reports have fuelled debate on Wall Street over whether the market is, indeed, maturing, even though year-to-year growth rates remain high. The volume of U.S. searches done through Google dropped to 5.86 billion from 6.14 billion in February, and the worldwide volume of searches also declined, comScore said.

According to analyst Youssef Squali of Jefferies & Co: “We are continuing to see deceleration in growth in Web search. Google’s month-over-month 5 percent decline is a little surprising, but all of the major Web search names were down.”

The decline was due in part to the month of February being two days shorter than January, comScore revealed. Yet several analysts believe it may also reflect a maturing market. By contrast, searches rose 9% in January over December. Amid this decline in the global market, Google shares closed off $7.16, or 1.6%, to $432, while Yahoo fell 59 cents, or 2.1% to $27.07.

The Reuters article also stated that investors have begun to focus on how well Google is converting Web searches into ad viewership.Analyst Mark Mahaney of Citigroup, on the other hand, blamed the company’s decelerating growth in recent months on the computer-based Web search market.