Google's share price fell 10 percent following disappointing results in the fourth quarter that saw the search giant miss its revenue target for the first time in eight quarters.
It was the first time Google has fallen short of Wall Street targets since Larry Page became CEO in April 2011, as he announced to investors on January 19 that fourth quarter revenue of $8.13b (£5.25b) fell short of the $8.41b estimate.
Having closed in New York at $639.57, Google's share price tumbled to $573 in after-hours trading.
Despite the number of clicks on adverts in search results increasing dramatically in the fourth quarter of 2011, the money Google charges advertisers for the ads decreased by eight percent over the three months.
City A.M. reports that Google "executives told investors on a conference call that foreign exchange movements were also to blame for the earnings miss."
Earnings per share for the quarter were $9.50, some way short of the $10.49 per share that analysts were expecting.
The news came on the same day that Google was named the best place to work in America by Fortune magazine.
But the news wasn't all bad, as the company reported that revenues for the year were up 29 percent and fourth quarter revenue - despite being down on expectations - was up 25 percent on the fourth quarter of 2010.
Page said: "Google had a really strong quarter ending a great year. Full year revenue was up 29 percent, and our quarterly revenue blew past the $10b mark for the first time.
"I am super excited about the growth of Android, Gmail, and Google+, which now has 90 [million] users globally - well over double what I announced just three months ago."
Although not mentioning Google's recent $12.5b acquisition of Motorola, Page said: "I'm very excited about what we can do in 2012 - there are tremendous opportunities to help users and grow our business."