Profit and revenue rose 29 percent in the quarter and at least twelve brokerages raised their price targets on the stock following Thursday's results.

But across technology circles the move by Google — founded during the first dot-com boom — to replace CEO Eric Schmidt with the 38-year-old Page left some wondering how the search giant would deal with middle age.

"Founder becoming CEO ... Is this like a Steve Jobs returning or a Jerry Yang returning?" Chris Dixon, a technology veteran who has invested in Skype and Foursquare, tweeted.

Steve Jobs returned to Apple Inc. in the 1990s to save the company he founded from near death. Yahoo Inc.'s Jerry Yang made a similar return, coming back to his Internet company during a troubled stretch — but has failed to restore its fortunes.

Starting in April, Google's Page will take over as chief executive, a move the company hopes will streamline its decision-making process amid fresh competition from Facebook and Twitter.

Shares of Google were up $2.53, or 0.4 percent, at $629.30 after opening at $639.58.

"It is important to note that although the titles have changed, the core team remains the same ... this new team structure makes a lot of sense and could result in faster decision making," JP Morgan analysts led by Imran Khan said.

Some analysts believe that Google's stock could gain another 20 percent from current levels.

Brokerage UBS said it was bullish on Google's long-term prospects and expects the company's focus on its emerging display network business, YouTube, Android and enterprise customers to deliver healthy returns in 2011.

Fourth-quarter operating margins were slightly weaker than expected at 53 percent on higher sales and marketing expenses.

JP Morgan's Khan, who lowered his 2011 operating margin estimates by less than a percentage point to 52.4 percent, said the expenses are necessary to promote future growth.

Evercore Partners, however, said it was still concerned about Facebook's present growth trajectory and deepening integration with third party sites.

Investors have speculated that Facebook could cut into Google's business if advertisers shift to the social network.

Shares of the Mountain View, California-based Google closed at $626.77 on Thursday on Nasdaq. They have risen 16 percent since Google reported third-quarter results mid-October and are up almost 45 percent from its 52-week low of $433.63 touched in July 2010.