The Nasdaq briefly topped 4,000 Monday for the first time since September 2000, but failed to close above that key level.
And while the tech-heavy Nasdaq did cross a big milestone, it is still well below its peak of above 5,000, which was set in March 2000.
Stocks ended mixed as investors took in a disappointing report on the housing market. Pending home sales dropped 0.6% in October from the prior month. That was the fifth straight decline. Economists expected a 1.3% increase. The housing recovery has been a big boon for the stock market this year, so signs of weakness are worrisome.
Meanwhile, investors seemed encouraged by a landmark deal reached between Iran and the United States, the United Kingdom, France, Russia, China and Germany over the weekend.
As part of the agreement, world powers will relax economic sanctions against Iran in exchange for a promise that the country scales back its nuclear program. Oil prices sank on the expectation of more oil exports from Iran following the nuclear deal.
World markets also climbed on the news. European markets finished with solid gains, with Germany's benchmark Dax index leading the way. Most Asian markets ended higher, with Japan's Nikkei jumping 1.5% as the yen weakened against the dollar.
Besides the Iran deal and pending home sales, there wasn't much other news moving markets. Trading volume is expected to be low during this holiday-shortened week and there are few economic and earnings reports on tap. U.S. markets will be closed Thursday for Thanksgiving and will shut at 1 p.m. ET on Friday.
In company news, Wal-Mart ( announced that current CEO of Wal-mart International D )oug McMillon will replace CEO Mike Duke, who plans to retire early next year. Shares rose and hit an all-time high.
Apple ( bought the Israeli tech company PrimeSense, a leading developer of 3D sensors. Apple's stock was up about 1%. )
Yahoo ( announced that K )atie Couric will join the company early next year as its "global anchor."
Social media stocks were trading lower, a sign that the hot sector may be losing momentum.
Shares of Yelp (, which have more than tripled this year, were down almost 7%. )Facebook ( shares, which have more than doubled so far in 2013, slid 3%. )
Twitter (, which just debuted on the stock market earlier this month, tumbled nearly 5%. )LinkedIn (, )Groupon ( and )Pandora ( were also all down sharply. That put pressure on the )Global X Social Media Index ETF (. )
Another user, ACInvestorBlog, noted that the fall of some "bubble stocks" could mean that Netflix ( and )Amazon ( could be next to face pressure. Netflix has surged 275% this year, while Amazon is up almost 50%. )
But some traders remained bullish on Facebook. One noted that Facebook's stock has enjoyed a sharp rally to its current level of around $45.