Virtually all of Chrome's April expansion came at the expense of Microsoft Corp.'s Internet Explorer, which dropped 0.7 percentage points to finish the month at 59.95%, the first time that IE has fallen under the 60% mark.... Mozilla Corp.'s open-source Firefox, on the other hand, was up last month, albeit by only 0.07 percentage points to 24.6%. April was the second month in a row that Firefox trended up, a victory of sorts in light of the fact that it had lost ground for four straight months starting in November 2009.