U.S. stocks fell Monday, reversing course after early gains. The Dow Jones industrial average fell 206.67, or 0.8 percent, to 25,819.65. The broader Standard & Poor's 500 index fell 10.88, or 0.4 percent, to 2,792.81. The technology-heavy Nasdaq composite index fell 17.79, or 0.2 percent, to 7,577.57.