Market trends often reverse on Fridays, as traders square up positions and book profits (or losses) ahead of the weekend. That was the case this holiday-shortened week, in which major averages stumbled in the wake of myriad profit warnings and disappointing guidance from Yahoo! ( YHOO).

Most of the high-profile warnings were in technology, starting Tuesday with Veritas ( VRTS) and Conextant ( CNXT), and continuing throughout the week from names such as PeopleSoft ( PSFT), Siebel ( SEBL), BMC Software ( BMC), and Unisys ( UIS).

In reaction to the negative preannouncements, the Nasdaq Composite fell 3% for the week. The Dow Jones Industrial Average lost 0.6%, while the S&P 500 declined 1% as Friday's modest rebound -- aided by raised guidance by SAP ( SAP) and solid earnings from General Electric ( GE) -- proved the exception to the market's decidedly downbeat rule.

The declines came as crude oil prices briefly climbed back above $40 per barrel, ending the week up 4% at $39.96. Meanwhile, gold surged back above $400 per ounce, ending the week up 2.6% to $407.90, as the dollar fell to a four-month low vs. the euro, which was trading at $124.14 late Friday.

In the absence of major economic data, Treasury prices were notably subdued; the yield on the benchmark 10-year note ended Friday at 4.46%, virtually unchanged for the week.

Weakness in shares -- particularly Tuesday's slide and the selloff Thursday afternoon -- caused technical damage, leaving stock proxies below their simple 50-day moving averages and the Comp below its 200-day moving average.

"We think that the U.S. equity market is potentially poised for its most significant selloff since the 2004 highs were put in place," commented Rick Bensignor, chief technical analyst at Morgan Stanley. "We remain cautious on putting new capital to work whenever the S&P 500 is anywhere above the 1130 area."

Bensignor's midweek report -- "The Market Shows Even More Vulnerability" -- correctly predicted weekly sell signals would be triggered Friday, based on Tom DeMark's Sequential Indicator, as the S&P closed below 1136.47 and the Comp below 1999. These are the first weekly sell signals since the March 2003 lows, he reported.

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