Among the sites recommended to keep material from are eBay, Facebook, Twitter, Tripadvisor and Rightmove.

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As a result, Rightmove.com seized the U.K., SeLoger France and Immobilien Germany.

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Part of the answer is that Rightmove displays only properties from estate agents, letting agents and new-home developers.

ECONOMIST: House sales go online

Leading the way is Rightmove, Britain's leading property website, which intends to list on London's stockmarket next week.

ECONOMIST: House sales go online

It is based on the prices that estate agents are asking for the properties they are advertising on the Rightmove website.

BBC: House price surveys explained

Rightmove explains that the price falls of the past few years mean that many people, who would like to sell, cannot afford to drop their prices.

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But Rightmove is determined to stay out of their clutches.

ECONOMIST: House sales go online

Most buyers and sellers, it seems, prefer to use an agent: Rightmove says that it now lists around seven out of ten of all properties for sale in Britain.

ECONOMIST: House sales go online

Rightmove's survey operates in a completely different way.

BBC: House price surveys explained