The stock market indices suffered a very negative setback today, with huge opening gaps to the downside. They then plunged to lower lows, and by mid-day reached their session lows on the Nasdaq 100. They attempted a snapback, which failed twice at resistance near 1850 NDX and 1094 S&P 500, and rolled over into the close with the SPX closing not far off the lows. The Dow was down as well. The Nasdaq 100 did fair a little bit better and closed about 7 points off its low, but still suffered a significant loss.

Net on the day, the Dow was down 265.42 at 10,378.83. The S&P 500 fell 31.59 at 1089.47, closing right at that 1088.90 key support zone. So tomorrow should be a very important day for the trend. The Nasdaq 100 was down 53.86 at 1845.38.

The technicals certainly confirmed the negative day, with declines leading advances by 6 to 1 on New York. Up/down volume was more than 30 to 1 negative, with a total of 1.150 billion shares traded. The vast majority of that, more than 95%, was to the downside.

Nasdaq was even worse with advance-declines at about 9 to 1 negative, and up/down volume nearly 22 to 1 negative. Total volume was a hefty 2 1/4 billion on Nasdaq.

TheTechTrader.com board was all negative, except for one stock and some of the ultra-short ETFs. That stock was portfolio position Netlist Inc. (NLST), which reported earnings after the close. It was up 7 cents at 3.05, just a few cents off its high for the day.

However, on the downside, multiple big-point losses included Cree Inc. (CREE), down 9.15 at 59.81, Apple Inc. (AAPL) 9.22 at 250.19, Google Inc. (GOOG) down nearly 12 at 491.74, Goldman Sachs (GS) 4.65 at 149.25, and Amazon.com Inc. (AMZN) down 4.11 at 125.89.

Other multiple-point losses were Transocean Ltd. (RIG) down 2.30 at 54.16, ADTRAN Inc. (ADTN) 1.51 at 30.21, Acme Packet, Inc. (APKT) 1.35 at 31.44, BP Exploration plc (BP) 1.32 at 38.79, Dendreon Corp. (DNDN) 1.74 at 36.90, OmniVision Technologies Inc. (OVTI) dropped 1.70 at 22, and Valassis Communications Inc. (VCI) 1.76 at 31.93.

There were several other point-plus losers, but too many to mention here.

On the plus side, the short ETFs had a stellar day as our day trade picks fared very well there. The Direxion Daily Emrg Mkts Bear 3X Shares (EDZ) was up 3.27 at 37.72, Direxion Daily Small Cap Bear 3X Shares (TZA) 3.68 at 35.75, iPath S&P 500 VIX Short-Term Futures ETN (VXX) 1.54 at 22.84, and Direxion Daily Financial Bear 3X Shares (FAZ) 1.37 at 14.98. In addition, the Direxion Daily Large Cap Bear 3X Shares (BGZ) advanced 1.16 at 14.92.

It was a very negative day on Wall Street, and a decisive crack of the recent 5-week uptrend. They closed right at key support levels near the 1840-45 zone on the NDX and the 1088-90 zone on the S&P 500.

Any downside follow-through tomorrow that cracks support could accelerate sharply, so it will be a very critical day to see how well the market fares and whether or not the downtrend is just beginning.

Harry Boxer is a technical consultant to many Wall Street hedge funds and large institutional traders, and author of TheTechTrader.com.