Stocks end mixed; worst day for Nasdaq since July 31

U.S. stocks were mixed on Monday, with technology shares slammed ahead of Alibaba's planned debut later in the week, as investors unloaded high-fliers a day before the Federal Reserve starts a two-day policy session.

"Today's the day when the Nasdaq is getting its due," said Bruce McCain, chief investment strategist at Key Private Bank, who noted that stocks leading the decline included "some of the names that have really run up the most."

"We are becoming a risk-aware market compared to where we were last year, and that's not a bad thing," added McCain.

Facebook was among the top decliners on the S&P 500, with the social network down 3.7 percent, curbing its year-to-date gain of 36 percent. TripAdvisor dropped 4.1 percent and Netflix declined 4 percent.

"It looks like some accounts may be raising cash by selling growth stocks," Elliot Spar, market strategist at Stifel, Nicolaus & Co., wrote in afternoon commentary.

"The market is feeling more tired than in the past. Take a look at the way we decelerated this year, we're up about 13 percent through June 30, versus earnings up about 9 percent. That's a lot more in balance than 30 percent gains last year versus 7 percent earnings," said McCain.

Molson Coors Brewing rallied on merger activity among brewers; Yahoo, which holds a 23 percent stake in Alibaba, turned lower as China's biggest e-commerce company planned its initial public offering; Microsoft fell after saying it would acquire Mojang, the creator of the "Minecraft" video-game franchise, for $2.5 billion; Apple reversed lower after saying it had drawn a record four million first-day pre-orders for its iPhone 6 and iPhone 6 plus.

Read MoreAlibaba lone bright spot in yahoo's dark decade

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The Dow Jones Industrial Average rose 43.63 points, or 0.3 percent, to 17,031.14, with Pfizer leading blue-chip gains that extended to 19 of 30 components.

The S&P 500 dropped 1.41 point, or 0.1 percent, to 1,984.13, with energy the best performing and technology the hardest hit of its 10 sectors, after finishing at a multi-year record last Thursday.

Some traders pointed to an article in the Wall Street Journal as helping spur selling in tech, with the newspaper quoting venture capitalist Bill Gurley as saying Silicon Valley might have taken on more risk than it can handle during the past year.

The CBOE Volatility Index, a measure of investor uncertainty, rose 6.1 percent to 14.12.

The Nasdaq shed 48.70, or 1.1 percent, to 4,518.90.

For every share rising, two fell on the New York Stock Exchange, where 591 million shares traded. Composite volume neared 2.8 billion.

NYSE New York Stock Exchange traders markets
Brendan McDermid | Reuters

The dollar held steady against the currencies of major U.S. trading partners; the yield on the 10-year Treasury note fell 2 basis points to 2.588 percent.

On the New York Mercantile Exchange, oil futures rose 65 cents to $92.92 a barrel and gold futures for December delivery added $3.60 to $1,235.10 an ounce.

A report before Monday's open had the Fed Bank of New York's Empire State gauge of general business conditions climbing to 27.54 from 14.69 in August, with the current reading the highest since October 2009.

Separate data had U.S. manufacturing output falling for the first time in seven months in August.

"There are few real bears on the economy at this point, but there are still some who want to make a bullish outbreak, and there is too much slack to make that happen. Probably 3 percent is about as good as it gets," said McCain of real-growth GDP this year.

"When you see a very strong number, chances are that's an artifact," added McCain, who noted the same could be said of exceedingly poor economic readings such as the nonfarm payroll number of 142,000 for August.

The Federal Open Market Committee is expected to reiterate the view that the economic recovery remains on track and could offer a possible time frame of when it might start raising rates at the end of a two-day meeting on Wednesday.

On Friday, stocks fell, snapping a five-week win streak.

—By CNBC's Kate Gibson

Coming Up This Week:

Tuesday

Earnings: FactSet, Adobe Systems, Apogee

FOMC meeting begins

8:30 a.m.: PPI

9:00 a.m.: TIC data

Wednesday

Earnings: FedEx, General Mills, Lennar, Cracker Barrel, Clarcor, Herman Miller

8:30 a.m.: CPI

8:30 a.m.: Current account

10:00 a.m.: NAHB survey

2:00 p.m.: FOMC statement

2:30 p.m.: Fed Chair Janet Yellen briefing

Thursday

Scotland independence vote

Earnings: Oracle, Rite-Aid, IHS, Tibco, RedHat

Alibaba IPO pricing

8:30 a.m.: Initial claims

8:30 a.m.: Housing starts

10:00 a.m.: Philadelphia Fed survey

Friday

10:00 a.m.: Leading indicators

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