From Reuters:

China has squeaked by Britain by the tiniest of margins to become the world’s fourth-largest economy, according to the World Bank‘s latest calculations.

The World Bank said that by its official measure China produced $2.263825 trillion in output in 2005. That was just $94 million, or 0.004 percent, more than Britain.

China comfortably overtook Britain last year based on each country’s gross domestic product converted into U.S. dollars at current exchange rates.[Full Text]

See also:
China now 4th largest economy, says WB by China Daily.