Computerworld - As Microsoft Corp.'s Windows Vista and Apple Inc.'s Mac OS X continued to grow their share of the operating system market last month, Mozilla Corp.'s Firefox suffered its biggest-ever drop in usage, a Web metrics company reported.
By the end of May, Vista accounted for 3.74% of all operating systems on machines connecting to Net Applications Inc.'s clients' Web sites. The total share for Mac OS X -- which included older editions running on PowerPC processors, as well as Version 10.4, or "Tiger," on Intel-powered Macs -- was 6.46%. Vista was up about three quarters of a percentage point from April, while Mac OS X was up a quarter of a point.
Their gains came largely at the expense of earlier versions of Windows, such as Windows XP and Windows 2000, although Net Applications' "Other" category, which is essentially Linux, also faded slightly.
"So, is Microsoft still looking over their shoulders at the Mac OS user base?" said Vince Vizzaccaro, Net Applications' executive vice president of marketing and strategic relationships, in an e-mailed newsletter. "You bet."
Vizzaccaro also validated Microsoft's claim last month that it had shipped 40 million copies of Vista in the next-generation operating system's first 100 days. "People are adopting Vista at a fairly good clip," he said. "Those numbers certainly seem to add up."
Meanwhile, Firefox experienced it's largest slip in browser market share since Net Applications began tracking the open-source software in late 2004. Firefox's share fell from 15.42% in April to 14.54% last month. Its loss was mostly Internet Explorer's gain -- IE 7's share climbed by 0.70% -- although Apple's own Safari browser also benefited; its share was up 0.23% in May to 4.82%.
To complicate matters, both IE and Firefox now face Apple as a browser rival on Windows: A week ago, CEO Steve Jobs unveiled Apple's Safari for Windows. Net Applications, however, won't break out Windows' Safari numbers until the browser leaves beta in October.
"I downloaded it and immediately ran into several bugs, so we backed off," said Vizzaccaro.
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