By Philip Elmer-DeWitt

    Here’s the latest on the four-way browser race to dominate the mobile Web.

    The main contenders are

    • Apple’s (AAPL) Mobile Safari, running on the iPhone and iPod touch

    • Opera Software’s Opera Mobile, running on a variety of Microsoft’s (MSFT) Windows Mobile devices

    • Nokia’s (NOK) Web Browser, running on a variety of Symbian phones

    • Research in Motion’s (RIMM) BlackBerry Browser

    According to a report issued Tuesday by StatCounter, a Dublin-based Web tracking service, Opera Mobile is back on top, with a 24.6% worldwide share to Mobile Safari’s 22.3%.

    “Opera began the year in number one slot but iPhone overtook it in February. May saw Opera regain the number one position,” writes StatCounter CEO Aodhan Cullen. “It will be fascinating to watch how this battle plays out over the year.”

    The report was picked up by Reuters and eventually made its way to the front page of Techmeme.

    The problem, as the chart below suggests, is that StatCounter is comparing all the devices that run Windows Mobile with only one of the devices that run Mobile Safari. When the iPod touch is factored in to their numbers, Apple’s share rises to 37.2% — which puts it well in the lead.

    Things get even more complicated when StatCounter’s data are compared with rival Net Applications‘. As Stephen Withers reports today on ITWire.com, Net Applications’s May report showed the iPhone OS with a 65% share. Withers can’t explain the discrepancy entirely, but he makes a valiant effort.

    Chart courtesy of StatCounter. Annotated by Tech.Blorge.