ozmanjusri writes "Online market share of the dominant Windows operating system has taken its biggest monthly fall in years to drop below 90%, according to Net Applications Inc. Computerworld reports that Microsoft's flagship product has been steadily losing ground to Mac OS X and Linux, and is at its lowest ebb in the market since 1995. 'Mac OS X... [ended] the month at 8.9%. November was the third month running that Apple's operating system remained above 8%.' The stats show that while some customers are 'upgrading' from XP to Vista, many are jumping ship to Apple, while Linux is also steadily gaining ground. A Net Applications executive suggests the slide may be caused by many of the same factors that caused the fall in Internet Explorer use. 'The more home users who are online, using Macs and Firefox and Safari, the more those shares go up,' he said. November has more weekend days, as well Thanksgiving in the US, a result that emphasizes the importance of corporate sales to Microsoft."