The stock market's behavior is downright strange lately. Professionals with decades of market experience scratch their heads as the market falls to its lowest point of the year, then surges almost 7% in an afternoon—all for no apparent reason. What's hanging over the stock market these days is uncertainty. BusinessWeek asked stock market experts to identify the biggest unknowns facing investors. These factors will be crucial to clearing up a foggy outlook. Unfortunately, it could take months—if not years—to resolve them. 1. Will the market lows hold? On Nov. 13, the broad S&P 500 index and the tech-heavy Nasdaq composite dipped to their lowest points of the year. The Dow Jones industrial average got close, sliding below the key level of 8000. Then, however, buyers flooded the market and all three indices jumped more than 6%, ...