Google's flotation has helped drive demand for advertising

In its first earnings report since floating on the stock market, the firm said net profit was $52m (�28.4m) in the three months ending 30 September.

That topped Wall Street estimates and Google shares on the Nasdaq closed Friday up 15.4%.

Sales surged to $805.9m in the quarter, up from $393.9 million a year earlier.

Google's main service - its internet search - is free to users.

But the firm makes much of its money from selling advertising space keyed to the words for which its users search.

It also sells the use of its technology to companies who need to make either their websites, or their internal information systems, searchable.

Pleasant surprise

"They really surpassed most people's expectations by a really wide margin," said Marianne Wolk, an analyst at Susquehanna Financial Group.

Google's chief executive Eric Schmidt said that the company was "very pleased with the short run and our performance in the quarter".

Founders, Larry Page and Sergey Brin, have plenty to smile about

The company did not give any forecasts for future sales and profit growth, but did say that there are no signs of the dip in advertising demand predicted by some analysts.

"In our business we see no evidence of it," said Mr Schmidt. "People are shifting their sales dollars to this category."

He added that advert prices had not levelled off and he did not expect them to cool in the near future.

Earnings in the third quarter were hit by a number of one-off charges, including the settlement of a patent dispute with rival Yahoo.

Excluding the charges, Google made a profit of $125m in the quarter.