Online shopping deals giant Groupon on Monday posted a sound quarterly profit but saw its stock tumble nearly 20 percent due to a disappointing forecast for the months ahead. The Chicago-based firm reported a profit of $28.38 million on revenue that climbed 45 percent to $568.3 million in the quarter ended June 30. \"We had a solid quarter despite challenges in Europe and continued investment in technology and infrastructure,\" said Groupon chief executive Andrew Mason. \"We\'ve deepened our relationships with a growing base of merchants and customers worldwide.\" However, investors were unhappy with revenue that was less than analysts expected and a scaled back forecast for the current quarter. Groupon shares fell more than 20 percent to a new low but regained some ground, down 18.41 percent to $6.16 in after-market trading on the Nasdaq. The company made its stock market debut at $20 per share in November and peaked above $31 dollars a share. In February Groupon issued its first earnings report as a publicly traded company, saying it failed to turn a profit despite revenue nearly tripling from a year earlier. Groupon shares were listed on the Nasdaq on November 4 in a blockbuster public offering that raised a whopping $700 million and triggered fears that investors may be foolishly overvaluing hot Internet startups. Groupon, which rejected a $6 billion takeover offer from Google a year ago, has enjoyed phenomenal growth since its founding in 2008 but has been dogged by questions about its business model and accounting methods.