NEW YORK (CNN/Money) - Major U.S. markets opened mixed but as scheduled Friday, despite a wide-ranging blackout that left the Wall Street area and many major brokerage houses' Manhattan offices without power Friday morning.

The New York Stock Exchange, which is on Wall Street, and the Nasdaq electronic exchange both opened for business as normal at 9:30 a.m. ET. At 10:20 a.m. ET, the Dow Jones industrial average, the NASDAQ composite and the Standard and Poor's 500 were straddling the breakeven point.

Trading is expected to be light Friday. Many traders will have trouble getting to work with public transit very limited in the New York metropolitan area. New York Mayor Michael Bloomberg asked the public to treat Friday as a "snow day" and not go to work unless it was essential. But he was at the NYSE to ring the opening bell Friday.

Some of the traders present Friday never got home Thursday evening. The blackout hit just after Thursday's market close and disrupted the rush hour commute. One trader slept in front a restaurant on Broadway near the exchange and showed at his health club before reporting for work.

But some traders had it good -- they slept at the NYSE's private club above the exchange floor, which had emergency power.

NYSE officials said security at the exchange seemed normal despite the unusual circumstances.

It wasn't clear what effect the blackout would have on trading. One trader suggested the thin trading could leave the market lower once trading concluded. "There are less people here today," he said.

Besides the obvious problem, one trader pointed to the fact that it's a summer Friday, which are normally quiet anyway, as a reason for lackluster activity.

The American Stock Exchange, which is only a few blocks away from the NYSE Wall Street offices had a delayed opening due to problems cooling its trading floor. The New York Mercantile Exchange also announced a delayed opening and plans to close early.

Besides trying to weigh the impact of the nation's largest blackout, investors have some reports to weigh as trading begins. The government's measure of consumer prices rose about in line with the Briefing.com analysts' forecast. But while the overall price rise of 0.2 percent matched the consensus, the 0.2 percent rise in prices excluding food and energy was above the 0.1 percent forecast for the so-called "core-CPI."

One positive for the tech sector that might be overlooked because of the blackout is Dell Computer (DELL: Research, Estimates)'s earnings and forecast. The PC maker posted higher fiscal second-quarter earnings that met the estimates of analysts surveyed by First Call, and raised its sales forecast for the current quarter. Dell shares were slightly higher in early trading Friday after opening slightly lower than Thursday's close.

But investors will not be able to get the latest reading of consumer confidence from the University of Michigan. The school said Friday that its report scheduled for Friday morning would be delayed until Tuesday due to the blackout, which also hit Michigan Thursday night.  

Reuters contributed to this report