Today's 3 Worst Stocks in the S&P 500

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.

The stock market has been the gift that keeps giving in 2013, and it continued its remarkable year by hitting fresh all-time highs just a day after Christmas. Strong retail data, and declining jobless claims, sparked today's rally, as filings for unemployment benefits slumped from 380,000 to 338,000 last week, an 11% decrease that underlines the U.S. economy's recovering labor markets. The S&P 500 Index added eight points, or 0.5%, to end at 1,842, a record closing high. 

Ironically, online retailer eBay ended as the S&P's single worst performer on Thursday, slumping 2% after the third week of December sales failed to match revenue in December's second week. Declining sales in the period leading up to online retail's most anticipated time of year is about the last thing you'd want to see as an eBay investor, and overshadows any progress the company might have seen this year from its PayPal service. Personally, I have a hard time believing that one week of subpar sales threatens eBay's position as a leader in online retail, but with little more to go on, Wall Street sold off the stock today. 

Shares of NVIDIA , which makes PC graphics chips and system-on-a-chip processors for mobile devices, slipped 1% in trading today. NVIDIA's Tegra business division, which, in a nutshell, focuses on the mobile side of the market, hasn't been as successful as some investors had hoped. In fact, it has churned out nothing but losses so far this fiscal year. Success in this burgeoning and highly competitive industry doesn't come overnight, however, and certainly doesn't come without significant investment. It remains to be seen what Tegra's future will hold, but I applaud the company for its long-term vision; if NVIDIA can capture even a small piece of the ever-growing pie that is the mobile market, patient investors could be primed for some heady gains down the line. 

Lastly, cloud performance service provider Akamai Technologies saw shares fall 0.9% Thursday. A "sell-off" of less than 1% is hardly anything to lose sleep over, especially when volume was about 50% lighter than an average day. Something I might worry about, though, if I were an Akamai shareholder, is the increasingly tough competition in Akamai's line of business, as the $8.5 billion company goes up against corporate behemoths like Verizon and Amazon.com. Verizon just acquired EdgeCast -- a company that streams video, houses web content, and improves download speeds -- earlier this month, an acquisition that reportedly cost the telecom more than $350 million.