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.

Stocks fell for the third straight day today, and the Dow Jones Industrial Average (^DJI -1.78%) had its worst session in nearly a month as concerns mounted about the Federal Reserve stimulus taper and a disappointing holiday season. The blue chips fell 94 points, or 0.6%, ending the day at 15,915.

With the Fed set to hold its next Open Market Committee meeting in two weeks to determine the future of its $85 billion bond-buying program, investors once again became nervous about the coming taper. Recent jobs numbers have been strong, and Friday's November jobs report should go a long way to determining monetary policy. Another month of strong employment growth could mean the Fed begins cutting the stimulus sooner than expected. Stocks have gained more than 25% this year in large part because of the Fed's bond-buying program, which have made bond yields artificially low, making stocks look better by comparison. Tomorrow's jobs report from ADP will be the first hint at how many new jobs were created in November.

Sales for yesterday's "Cyber Monday," the day online retailers promote for holiday shopping, jumped 16% to $2.29 billion, though shares of Amazon.com (AMZN -2.98%), the world's biggest online retailer, fell 2% on news that delivery companies such as UPS are also testing delivery drones, an idea that Amazon.com CEO Jeff Bezos mentioned in an interview on 60 Minutes Sunday night.

Meanwhile, Tesla Motors (TSLA 1.71%) shares shot up 16% after a German regulatory agency said it didn't find any manufacturer defects in the electric-car maker's Model S Sedan, which had come under scrutiny after three fires were reported in the vehicles in a span of just six weeks. The car is still under investigation by the U.S. National Highway Transportation Safety Board, but the German board's ruling goes a long way to reassuring the public about the vehicle's safety and the market about any serious recall concerns.

Elsewhere in the auto industry, November sales jumped to an annual rate of 16.4 million, up from 15.3 million a year ago, the best figure since February 2007, a strong sign for the overall economy and for carmakers.

Sears Holdings (SHLDQ) shares continued to fall, dropping 7.7%, continuing a two-day slide of 13% on poor Black Friday results. Sears had been one of the most aggressive Black Friday marketers, as its Kmart stores were open for 41 hours straight.