Taco Cowboy writes with news that Microsoft's stock price dropped over 11 percent yesterday. The selloff was the biggest since 2009, and during the day the price was down more than 12 percent at one point, making it the biggest single day drop since April, 2000. Analysts believe the drop was due primarily to the company missing its quarterly earnings projections in addition to taking a massive, $900 million write-down on unsold Surface RT tablets. "Microsoft’s decline is both a consequence of the changing dynamics of the tech world and the incredible surge in its stock price this year. Shares in the maker of Windows had rallied nearly 30% this year, leaving both the broader stock market and the technology sector in the dust. It was, it seemed, Steve Ballmer’s year. Until Friday. The sell off was sparked by fears over the declines of the PC market. Gartner data show PC shipments fell for the fifth consecutive quarter in Q2, this time tanking 10.9% to 76 million units. Being the world’s largest software company, 'over 80% of its revenue and nearly all of its profits continue to be derived by its ubiquitous Windows OS, its server business (Windows Server), and the business division (Office),' according to UBS. And indeed that decline in the PC industry is hurting the company’s bottom line."