But older editions of IE dropped by more than what IE9 gained.

IE6, the browser Microsoft wants to kill, fell by four-tenths of a point to 11%, while IE7 slipped by two-tenths of a percentage point to 7.9%. And IE8, until last month Microsoft's current browser, dropped half a point to end March at 34.4%.

IE8's slip was the first for that browser since Net Applications began tracking it three years ago, a full year before it shipped in final form in March 2009.

Some rivals, meanwhile, continued to gain share at Microsoft's expense.

Google's Chrome grew its share by six-tenths of a point to account for 11.6% of all browsers used worldwide last month, a record. And Apple's Safari posted a gain of three-tenths of a point to end the month at 6.6%.