European and US stocks have fallen, in one of the worst qarterly falls for the markets in the past decade.br br Stocks dropped broadly on Friday in fresh signs that Europe's debt problems and the US economy continue to languish.br br The Dow Jones, Standard & Poors (S&P) 500 and Nasdaq each lost more than 12 percent this quarter, the first time that's happened since the financial crisis crested at the end of 2008.