WPP, the FTSE 100 advertising firm, has agreed to take a majority stake in the Chinese digital agency A4A.Founded in 2003 and based in Beijing, A4A's offering includes digital strategy, social media and online advertising. A4A's revenues for 2010 were approximately £1.6m. The agency's client list includes Audi, Lenovo, Mamibuy and Nokia. WPP is already well represented in the greater China region, with revenues of $1bn and 12,000 employees. BS