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

Welcome back to the bizarre market where up is down, and good means bad!

The broad-based S&P 500 (^GSPC 1.17%) suffered its worst losses in a month after initial third-quarter GDP data revealed that the U.S. economy grew by 2.8%, handily surpassing the 2.5% growth registered in the second quarter, and far higher than the forecasted GDP growth, which ranged between 1.9% and 2.5% among economists. While better-than-expected growth should be what investors strive to see, strong GDP growth could be a death knell for the Federal Reserve's quantitative easing program, which is injecting $85 billion each month into the economy. With tapering fears back on the table, investors are taking the opportunity to hit the exits.

We also had relatively tame weekly jobless claims data today. For the week, initial jobless claims fell 9,000, to a seasonally adjusted 336,000, which is more or less in line with expectations. The good news here is that, as long as jobless claims remain in the low-to-mid 300,000 range, we can probably expect the unemployment rate to continue to fall. On the downside, though, a falling unemployment rate is another excuse for the Fed to taper QE3.

By day's end, investors gave the S&P 500 quite a beating, with the iconic index losing 23.34 points (-1.32%), to close at 1,747.15, its lowest close in the past 11 trading sessions.

Leading all stocks within the S&P 500 to the upside today, with a 5.6% gain, was struggling retailer J.C. Penney (JCPN.Q), which reported an October same-store sales increase of 0.9%. That's right... I did say an increase! This marks the first time in 23 months that same-store sales have increased over the previous year; but the company still warned that it has needed to discount heavily to move excess inventory. In other words, sales are finally stabilizing a bit, but the underlying fundamentals are just as ugly now as they were last quarter. Penney's isn't offering even the slightest glimpse of a profit anytime soon, and I would still suggest keeping a safe distance from this struggling retailer.

Insurance and investment management company Prudential Financial (PRU 0.11%) tacked on 2.4% after the company reported its first profitable quarter in the past five quarters. Overall, revenue fell 18%, to $10.8 billion, well below forecasts which had called for $11.9 billion, but the company was able to deliver a $2.07 per-share profit, which is well ahead of the $1.34 per share loss reported in the year-ago period. Even though this figure, too, fell short of estimates by $0.04, I believe shareholders are simply thrilled to see Prudential back in the black. With annuity and retirement account values up by double digits, I'd say that Prudential's forward P/E of nine certainly makes it worth a look for financial sector-savvy investors.

Finally, industrial automation power, control, and information solutions provider Rockwell Automation (ROK 1.85%) advanced 2.3% after delivering strong fourth-quarter earnings results. For the quarter, Rockwell reported a 3% increase in year-over-year sales, to $1.72 billion, with its architecture and software business delivering the biggest kick, up 6%. Net income rose 10% from the previous year to an adjusted profit of $1.53, $0.01 ahead of the Street's expectations. Looking ahead, Rockwell guided investors to a full-year profit of $5.95-$6.35, which is right in line with the $6.15 consensus. While Rockwell's international business is helping to buoy sales, I remain concerned that domestic austerity measures could hamper Rockwell's growth, and, as such, would keep any lofty expectations for the company in check.