Technology stocks are dropping for a second day in a row as investors flee highflying Internet and biotechnology companies.
The Nasdaq composite closed out its third losing week in a row.
The Nasdaq lost 54 points, or 1.3 percent, to end at 3,999 Friday. It was only the second time this year the index has closed below 4,000. It's down 8 percent from the high it reached in early March.
The Standard & Poor's 500 fell 17 points, or 1 percent, to 1,815. The Dow Jones industrial average fell 143 points, or 0.9 percent, to 16,026.
JPMorgan Chase fell 4 percent after reporting weaker earnings. Other big banks also fell, including Bank of America.