Once again in February, Google (GOOG) expands its lead in U.S. internet search - at the expense of Yahoo (YHOO), Microsoft (MSFT), and Ask.com (IACI). According to Hitwise, GOOG captured 72.1% of the market, up from 66.5% a year ago. YHOO 17% vs. 20.6%. MSFT 5.6% vs. 7%. Ask.com 3.7% vs. 4.1%.