The indices had a strange, mixed session today, but they rallied strongly in the morning after a sharp gap down at the opening failed to have any follow-through at all. In that rally the Nasdaq 100 moved from 1942 to 1981, almost 40 points just in the morning session. The S&P 500 at that point rallied from 1451 to 1468 and trailed a bit at that point. But, a sharp pullback ensued just before lunch hour on some news of a potential terrorist problem at the UN, and when that proved to be minor the indices rallied back but failed to take out the highs. Then they rolled over even more sharply, taking out the earlier pullback lows and testing the session lows on the S&P and the early part of the morning lows on the NDX. However, the 2-day uptrend line did hold and they bounced late in the session.

Net on the day the Dow was down 50 1/2, the S&P 500 a little more than 6, but the Nasdaq 100 was up nearly 9. The Philadelphia Semiconductor Index (SOXX) advanced 0.75.

Advance-declines, however, were negative for most of the session and ended 3 to 2 on the downside on both indices. Up/down volume was also negative by more than 2 to 1 on New York and positive by about 2 to 1 on Nasdaq. Total volume was lighter today, less than 1.3 billion on New York and about 1 2/3 billion on Nasdaq.

TheTechTrader.com board was narrowly mixed, but there were some strong gainers. By far the star of the day was Sigma Designs (SIGM), soaring 4.07 on more than 10 1/2 million shares, the heaviest volume in its history. At one point it traded even 3 points higher than that during the day, at 45.59, and sold off 3 points in the afternoon on profit-taking.

Chindex (CHDX) had an outstanding today, up 2.61 to 19.95, the strongest 1-day gain since January for that stock. Eschelon Corp. (ELON) gained 2.26, DryShips (DRYS) 1.09, Excel Maritime (EXM) 1.48, LDK 1.86, TASR 71 cents, and SCON 69 cents, trading more than 10 million shares today.

Harmonic (HLIT), a new one we're following, was up 63 cents, and Bluephoenix (BPHX) gained 44 cents.

On the downside, Aluminum Corp. of China (ACH) was the big loser today, down 3.48. FuelTek (FTEK) gave back 81 cents, Global Solutions (GSOL) 59 cents, and Nuance Communications (NUAN) 34 cents.

Stepping back and reviewing the hourly chart patterns, they made new rally highs on the Nasdaq 100 but failed to do so on the S&P 500, and that may have been part of the reason, without confirmation from the S&P and the Dow, that the indices rolled over in the afternoon.

We'll see if that rollover means anything, but it did look like a fairly orderly stair-step decline, so we'll see how it goes over the next couple days.

Harry Boxer is a technical consultant to many Wall Street hedge funds and large institutional traders, and author of TheTechTrader.com, a real-time diary of his day, swing and intermediate-term trades. For more of Harry Boxer, sign up for a free 15-day trial to his Real-Time Technical Trading Diary, or sign up for a free 30-day trial to his Top Charts of the Week service.