Stocks mostly rose today as remarks from Federal Reserve Chairwoman Janet Yellen signaled that the central bank was committed to supporting the economy in its recovery as it continues to taper its bond-buying program. The Dow Jones Industrial Average (DJINDICES:^DJI) finished up 118 points, or 0.7%, and the S&P 500 finished up 0.6%, though the Nasdaq sank 0.3% on a sell-off in the tech sector. At one point, the tech-heavy index was down as much as 1.5% as Alibaba filed for its IPO, drawing money out of other tech stocks, but rose late in the session to recover most of its losses.

In comments to the Congressional Joint Economic Committee, Yellen said there was still "considerable slack" in the labor market, and that a flattening housing market and geopolitical tensions pose risks to the U.S. economy that warrant the Fed's attention. Stocks rose broadly after her remarks, as she said the economy was on track for solid growth this quarter, and investors were glad to hear that she planned to keep benchmark interest rates near zero in order to boost the economic recovery. 

Among stocks making news after hours was Tesla Motors (NASDAQ:TSLA), which fell 7.6% after reporting earnings. The electric-vehicle maker actually beat earnings estimates, posting an adjusted per-share profit of $0.12 against $0.10, and revenue grew 27% to $721 million, also beating estimates of $699.1 million. However, the company warned that free cash flow would run slightly negative this year because of starting construction on a lithium-ion battery plant, known as the "Gigafactory." Vehicle deliveries in the quarter of 6,457 were in line with guidance at 6,400, and the company forecast 7,500 vehicles for the current quarter. There seemed to be little in the report to warrant such a sharp sell-off, but the drop may have come from the market's realization that not every quarter will be a blowout for Tesla. At a P/E over 200, the company may need to significantly exceed expectations to move higher.  

Elsewhere, Keurig Green Mountain (NASDAQ:GMCR) shares were heating up, gaining 6.7% in the extended session. The maker of the pod-based coffee brewer said sales grew 10% to $1.1 billion, breezing past estimates at $1.05 billion, as both portion packs and brewer systems showed steady growth. On the bottom line, adjusted earnings per share scooted up 16% to $1.08, easily topping the consensus at $0.94. Looking ahead, the company sees earnings per share of $3.63 to $3.73, though that guidance takes into account a negative impact of $0.20 resulting from share dilution from its recent deals with Coca-Cola and Lavazza, and $0.09 for foreign currency translation. Analysts had expected a profit of $3.72 per share. Though the days of Keurig's skyrocketing growth are gone, the company has proved it can still grow after losing many of its portion-pack patents in 2012. Excitement about the Keurig Cold brewing system and the company's partnership with Coke is likely to keep shares elevated through 2015, when the new system comes out.