The Dow Jones industrial average fell 11 points, or 0.1 percent, to 12,198 shortly after noon. The Dow surged 339 points the day before, its biggest gain since Aug. 11. The Dow is headed for its biggest monthly gain since 1987.
"It's a kind of sobering-up after a day of partying," said Jerry Webman, chief economist with Oppenheimer Funds in New York.
European leaders unveiled a plan early Thursday to expand their regional bailout fund and force banks to keep bigger cash buffers. Banks agreed to forgive half of Greece's debt. The Dow and the Standard & Poor's 500 index both gained more than 3 percent.
Optimism ebbed on Friday as analysts raised questions about the plan, which lacks many key details. It is not yet clear how the rescue fund will work, for example. European markets mostly fell, and the euro declined against the dollar.
"We got back to what's more of a square position, closer to where we want to be, and now we're going to take a couple of deep breaths and reassess what this really means," Webman said. He said there are still plenty of obstacles to overcome before the crisis is resolved.
One troubling sign: Borrowing costs for Italy and Spain increased, signaling that traders remain worried about their finances.
The S&P 500 index lost 4 points, or 0.3 percent, to 1,281. Of the S&P's 10 industry groups, only three rose: materials, telecommunications and health care.
The Nasdaq composite index slipped 11 points, or 0.4 percent, to 2,728.
The Dow is up 11.8 percent this month, the S&P 13.2 percent. Both indexes are on pace to have their best month since January 1987.
In less than four weeks, the Dow has risen 14.5 percent from its 2011 low, reached on Oct. 3. The S&P has gained 16.6 percent in that time. However, the Dow remains 4.8 percent below this year's high, reached on April 29. The S&P is 6.1 percent below its high.
Whirlpool Corp. slumped 12 percent, the most in the S&P index, after the appliance maker said it would cut 5,000 jobs, citing weak demand and higher costs for materials. Another household name, Newell Rubbermaid Inc., soared 12 percent after its adjusted earnings beat Wall Street's expectations. The maker of tubs and markers maintained its outlook for the year.
Cablevision Systems Corp. fell 15 percent, the most in the S&P 500, after reporting that its third-quarter net income dropped sharply and it lost cable TV subscribers.
Thursday's stock rally led to a sell-off in Treasurys, which traders hold to protect their money when other investments are falling. Demand for Treasurys increased sharply Friday, pushing the yield on the 10-year Treasury down to 2.30 percent from 2.39 percent late Thursday.
Markets have been roiled for months by fears about the impact of Europe's debt crisis. Greece couldn't afford to repay its lenders, and banks holding Greek bonds faced billions in losses. A disorganized default by Greece threatened to spook lenders to other countries with heavy debt loads such as Spain and Italy. Traders feared that a wave of defaults by countries would cause financial panic and mire the global economy.
Some analysts expect traders to refocus on U.S. economic news next week after months spent watching Europe. The government releases its jobs report for October next Friday. A news conference by Federal Reserve Chairman Ben Bernanke might offer clues about the Fed's economic outlook. Key reports on manufacturing and business sentiment are due out as well.