Reporting for the first time as a public company, career-oriented social network LinkedIn posted strong membership growth and better-than-expected quarterly revenue on Thursday.LinkedIn, which began trading on the New York Stock Exchange in May, said net profit rose to $4.51 million in the second quarter from $938,000 during the same quarter a year ago. Revenue soared 120 percent to $121 million. Wall Street analysts had forecast revenue of around $104.5 million for the quarter ending June 30.LinkedIn said membership grew 61 percent to 115.8 million and it had 81.8 million unique visitors per month, an increase of 83 percent from a year ago.\"In the second quarter, we saw record levels of members, unique visitors, and page views, while revenue growth further accelerated,\" LinkedIn chief executive Jeff Weiner said in a statement.\"Going forward, we plan to continue to invest in our team, technology and products in order to increase the value we deliver to members and realize the full potential of the LinkedIn platform.\"LinkedIn said it expects revenue of between $121 million to $125 million in the current quarter.The firm, which began trading in May at $45, lost 9.59 percent on Wednesday to close at $95.52 as Wall Street suffered its worst one-day drop in more than two years. But LinkedIn shares rebounded in after-hours trading after the company\'s quarterly results were released, gaining 4.70 percent to $100.01.