Stocks hit a big milestone then slipped back. On Monday — the first trading day after the Dow closed at its highest since the financial crisis — major indexes fell the most this year. Friday was only the 10th time the Dow had closed above 14,000. The first time was in July 2007; the rest were in October of that year. On Friday, the Dow was just 155 shy of its record high after a rally driven by stronger economic data, especially on jobs and manufacturing. But on Monday US stocks followed European markets lower. Europe’s problems are again affecting US markets after several quiet months, said Bill Stone, at PNC Asset Management.