Although we don't believe in timing the market or panicking over daily movements, we do like to keep an eye on market changes -- just in case they're material to our investing thesis.

U.S. indexes slumped Tuesday as two issues fell for every one that advanced in the stock market today. Tomorrow Wall Street will turn its eyes to retail sales, the consumer price index, and existing home sales for guidance; today's market was driven by earnings and anticipation of Federal Reserve Chairman Ben Bernanke's comments this evening. The Fed has been a huge driver in equity markets this year, most recently shocking the "smart money" by continuing its $85 billion monthly quantitative easing efforts in its September meeting. The S&P 500 Index (SNPINDEX:^GSPC) shed three points, or 0.2%, to end at 1,787 today as investors turned their eyes from central bank policies to corporate earnings. 

Far and away the most beleaguered stock in the S&P 500 was Best Buy (NYSE:BBY), which cratered 11% Tuesday, bucking the year's bull run, which has seen shares more than triple in 2013 alone. The sudden slump came under strange circumstances: Best Buy exceeded profit expectations in the third quarter, while matching Wall Street revenue projections. The real doozy was a result of fourth-quarter expectations, which CEO Hubert Joly did his darnedest to temper dramatically. Best Buy will take a page out of's book, sacrificing profits and margins for market share this holiday season. It's certainly not a move short-term investors are cheering, but for the long-term investor, this looks like a bold step in the right direction.

San Jose-based chipmaker Altera (NASDAQ:ALTR) stumbled 4.3% after Goldman Sachs removed shares from its conviction buy list. Goldman retained its "buy" rating on the stock, but lost some faith in the company after it literally failed to provide any sales guidance for next year. Wall Street, understandably, prefers to have concrete figures to work with so it knows what to expect going forward. 

Finally, solar semiconductor producer First Solar (NASDAQ:FSLR) lost 3.9% in trading as the entire solar industry took a turn for the worse. Rightly or wrongly, stocks in emerging industries like solar technology today or dot-coms in the 1990s often move together as a group, since the businesses themselves are young and the future is wildly uncertain. First Solar fell victim to this dynamic today, as Chinese competitors Yingli Green Energy and JinkoSolar fell 10% and 6%, respectively, after earnings. First Solar is the only one in the group turning a profit, so today's decline doesn't really signal a core incompetency in the business model or anything dire. 

Fool contributor John Divine has no position in any stocks mentioned. You can follow him on Twitter @divinebizkid and on Motley Fool CAPS @TMFDivine.

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