ISDEX Speeding South

Just a few weeks ago, internet.com’s Internet Stock Index was on a jagged but determined march north, coming within a few percentage points of finishing in the black for the first time since April 7.

Today, the ISDEX is traveling a much straighter road. Unfortunately, it’s headed due south. And unless it can reverse direction soon, the index stands a good chance of reaching new lows in 2000 well before Halloween.

The ISDEX fell 12.6% to 630 in the week of trading ended Wednesday, with 44 of its 50 members losing ground. In comparison, the Nasdaq plunged 10.1% to 3168.

If the ISDEX falls just 6% more from Wednesday’s finish, it will erase the current low closing price for the year of 592.61 set on May 26.

For the year, the ISDEX is down 16.2% from its Dec. 31 close of 860.35, while the Nasdaq is off 22.1%.

Swimming strongly against the red tide this week was RSA Security , which gained 25.2% after 1) bouncing off its lowest closing price of the year on Oct. 4, and 2) announcing, on the same day, that third-quarter results would beat street estimates for earnings and revenue.

The Massachusetts-based maker of authentication, encryption and digital certificate management software expects to report Q3 revenues of $72 million, up 29% from the year-ago quarter. RSA said Q3 net earnings from its security products will be 24 cents per diluted share, up from 18 cents a year ago. Analysts have forecasted earnings of 23 cents per share.

The company also said it would repurchase up to 4 million shares of its common stock over the next 12 months. RSA is expected to release its Q3 earnings report after the market closes on Thursday.

Only three other ISDEX companies turned in double-digit gains this week. E-business software vendor Vignette bounced off its lowest closing price of the year ($18.69) on Friday as bargain-hunters entered the fray on Monday, driving up VIGN shares 39.8% in just one session.

A new alliance between e-commerce sales software seller BroadVision and supply-chain software vendor i2 Technologies boosted shares of both companies on Monday. The firms plan to develop software packages designed to allow customers to combine online ordering with inventory management. BVSN rose 10.8% this week, while ITWO climbed 10.4%.

The week’s biggest ISDEX loser was “name your price” e-tailer priceline.com , which continues to stagger in the wake of bad press and a Q3 earnings warning. PCLN dropped 42% this week, and is down 80.5% in the past month. Name your price has become name your poison.