At the top of some 4.7 million results are paid advertisements, which are marked by a tiny yellow "Ad" mention before the link, while more line the right-hand column.

Their appearance there is not by chance: those websites paid Google's advertising unit Adwords to appear where eyeballs first fall.

Companies can "buy" keywords using an auction system, with those paying the most usually ending up the highest in the ranking, explained Jonathan Vidor, head of the Jvweb company that helps firms precisely target customers via search engines.

He said that in France each click by a customer through a paid Google link is worth between 0.70 and 0.80 euros.

But those paid search results is not what bothers the European Commission, which announced Wednesday it had sent Google a formal "Statement of Objections" that could see it face a fine of up to 10 percent of annual sales that came to $66 billion last year.

Instead the Commission takes issue with Google listing right below the paid ads Google Flight, its own air ticket price comparison search service, before any natural results of its search engine.

Thus Google is placing its services ahead of rival services offered by companies such as Expedia, Edreams, Opodo or Ebookers.

It was Expedia, along with Microsoft, Oracle and Tripadvisor that filed a complaint against Google at the end of 2010 with EU competition authorities.

After years of discussions with Google that failed to end in an amicable settlement, the Commission went on the attack Wednesday by accusing it of "systematically favouring its own comparison shopping product in its general search results pages."

For the search for Paris to Berlin air tickets is far from being alone: whether searching for red pants, a hotel in Sydney, or a washing machine, the results will feature prominently Google's Shopping and Hotel Finder services.

In the same way, searches for locations offer Google Maps and translation requests promote Google Translate.

- 'Ecosystem of services' -

"Google was historically a search engine, but today it is an ecosystem of services," said Olivier Ertzscheid, a lecturer at the University of Nantes in France.

"Companies on the Internet have no other model than to put their own services first" he said.

He said the Commission's argument was akin to criticising a supermarket chain for not mentioning the existence of rivals in their stores.

"The problem is one of transparency: when you go onto Google you are not necessarily aware there are competitors."

And Google enjoys a super-dominant position in Europe, accounting for 90 percent of Internet searches.

"Bing, for example, does similar things but no one complains," said Vidor, referring to the Microsoft search engine.

There are also concerns about the secret algorithm Google uses to generate the regular search results.

In the past "certain competitors noticed that once the algorithm changed, their web traffic dropped by 30 percent," said Cyril Brosset, of the consumer protection group UFC-Que Choisir.

"One hopes that Google modifies its algorithm in the interest of consumers, but its competitors fear they use it to lower the ranking of other price comparison sites," he added.

Brosset said what needs to be avoided is the situation where people believe Google is the Internet.

"It is a way to access certain content," he said. "Google makes its rankings and it isn't always neutral."

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