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In this May 16, 2012 photo, the Facebook logo is displayed on an iPad in Philadelphia. Facebook's stock has fallen below $30 for the first time. That's down 20 percent since its stock began trading publicly on May 18, following one of the most anticipated stock offerings in history. (AP Photo/Matt Rourke)

Today: Facebook and other social media stocks close out a better week, possibly indicating their struggling shares have found a floor. Also: Wall Street also gains Friday, as Apple (AAPL) closes at highest price in a month ahead of WWDC.

Facebook closes out calmer week with gain, as Yelp rebounds strongly

Friday marked three weeks since Facebook's heavily anticipated and record-breaking initial public offering, and the world's most popular social network has fallen hard on Wall Street in that time, taking other social-media stocks down with it. However, positive movement for Facebook shares and an incredibly large leap by San Francisco online-reviews site Yelp on Friday could signal a rebound for the struggling tech sector.

Facebook stock rose 3 percent Friday to close at its highest price of the week, at $27.10, and it matched the highest intraday mark of the week at $27.76. It was the second solid gain of the week for Facebook stock, following a bounce in Wednesday's session, and comes as the company announced a new app store that will offer games and software with recommendations from a user's circle of friends.

Facebook may have been helped more from an outside source, though: Digital metrics company ComScore reported Friday that its research showed that ads on the social network are effective at engaging users, going against a popular theme circulating since General Motors decided to pull its ads from the Menlo Park company's site in the run-up to its IPO. The thought that Facebook ads do not sway the social network's 900 million users was given credence by a Reuters poll earlier this week that showed four out of five Facebook users had never interacted with a company through a Facebook ad.

ComScore downplayed the Reuters story, saying simple polling is useless in determining advertising effectiveness, and said its newest report shows "Facebook earned media is having a statistically significant positive lift on people's purchasing of a brand." Little else was said in the company's blog post, as it expects to release the full report on Facebook's effectiveness Tuesday at a conference in New York.

The two developments could be cheering investors, who have been concerned about Facebook's ability to increase its advertising revenue, as well as its lack of other avenues for cash. Facebook's App Center could push more money to the site directly from users, and a more positive view of Facebook advertising could help dull the effect of GM's pullout and the reams of doubters.

Still, Facebook has descended 28.7 percent from its IPO price of $38 a share at the end of three weeks of trading, and the doubts stemming from the fall have led other social media stocks down.

One of those stocks managed a huge rebound Friday, however. Yelp's stock ended the day up 12.1 percent, on the heels of a 6.4 percent rise Thursday and an 8.2 percent increase Wednesday. Before those three days of large gains, Yelp had descended 28.4 percent since Facebook began trading on the Nasdaq stock exchange.

There was little news to justify a big increase in Yelp's stock price, though the San Francisco company did continue its international expansion efforts by launching in Finland this week. Some analysts believe that the leap could be a result of too many investors seeking to "short," or bet against, Yelp's performance on Wall Street.

Mountain View professional-networking site LinkedIn and San Francisco online-gaming company (and Facebook partner) Zynga also managed gains Friday, though not as large as Yelp's leap. LinkedIn, despite negative publicity from the theft of millions of passwords earlier this week, gained 2.3 percent Friday, while Zynga advanced 0.3 percent.

As a whole, social media companies may have finally reached a floor with their performance this week after being mauled by investors since Facebook's IPO. From the beginning of Facebook's first day of trading on May 18 through the close of last Friday's trading session, Facebook fell 27.1 percent; LinkedIn declined 12.8 percent; Zynga descended 27.3 percent; and Yelp went down 26.2 percent.

This week, however, Facebook's descent slowed markedly and the other three companies managed gains. Facebook stock fell 2.3 percent between the close of the June 1 session and Friday's close, while LinkedIn gained 5.2 percent, Zynga rose 0.7 percent, and Yelp jumped up 25.2 percent. While that performance came as Wall Street enjoyed its best week of 2012 so far, previous performance showed social-media stocks -- most of which are not included in the major indexes yet -- could act in a completely opposite fashion than the larger market.

Wall Street has best week of 2012, but Europe still scares investors

Speaking of the market's best week of 2012, it ended Friday with gains of almost 1 percent for all three major U.S. stock indexes as President Obama forcefully said that Greece should not dump the euro as its currency and a bailout for Spain neared reality.

Wall Street's performance continues to be tied to the daily news out of Europe, as fragile economies in Spain and Greece have the ability to paralyze financial systems worldwide.

"Europe is on the precipice. And the odds are uncomfortably high they go over the ledge," Mark Zandi, chief economist at Moody's Analytics, told the Associated Press. "If they don't (keep the eurozone together), then the European economy will sink deep in recession and take the rest of the global economy with it, including our own."

Fears about Europe did not keep U.S. stocks down this week, however, as the Dow Jones industrial average moved up 3.6 percent; the Nasdaq industrial average shot up 4 percent; and the Standard & Poor's 500 rose 3.7 percent. It was the best week of percentage gains for all three indexes since December, a needed development after May pulled stocks down.

Analysts believe a solution -- or even a band-aid -- for the European issue could drive stocks higher, completely wiping out May's losses.

"If we can just get any sort of clarity out of Europe ... even if it's not great news, just something to sort of hang our hat on ... we could potentially have a lot of buyers come into this market," Joe Bell, senior equity analyst at Schaeffer's Investment Research, told TheStreet.com.

Apple closes at highest price in a month ahead of WWDC

Apple stock received a bounce Friday that helped the Cupertino tech giant close at its highest price in more than a month ahead of expected announcements in San Francisco next week.

Apple shares advanced 1.5 percent Friday to close at $580.32, higher than any closing price since May 3. The company seems to have solidly escaped the doldrums it suffered in May, when its stock closed as low as $530 a share following weeks above $600.

Now, eyes turn to the company's World Wide Developers Conference, which begins Monday at the Moscone Center. Banners unfurled Friday revealed that Apple will, as expected, announce the newest iteration of its mobile operating system, iOS 6; the company is also expected to announce a map application to compete directly with Google (GOOG) Maps, as well as new MacBooks and other products.

For live coverage of WWDC beginning Monday morning, go to www.siliconvalley.com.

Silicon Valley tech stocks

Up: Yelp, Splunk, Tesla, Facebook, Advanced Micro Devices, LinkedIn, Juniper, Nvidia, Yahoo (YHOO), Intel (INTC), VMware, Netflix (NFLX), Apple, Gilead, Hewlett-Packard (HPQ), Adobe

Down: NetApp, SunPower (SPWRA), Jive, Oracle

The tech-heavy Nasdaq composite index: Up 27.40, or 0.97 percent, to 2,858.42

The blue chip Dow Jones industrial average: Up 93.24, or 0.75 percent, to 12,554.20

And the widely watched Standard & Poor's 500 index: Up 10.67, or 0.81 percent, to 1,325.66

Check in weekday afternoons for the 60-Second Business Break, a summary of news from Mercury News staff writers, The Associated Press, Bloomberg News and other wire services. Contact Jeremy C. Owens at 408-920-5876; follow him at Twitter.com/mercbizbreak.