BEIJING: Chinese regulators have imposed limits on the number of lucrative healthcare adverts carried by Baidu Inc following the death of a student who underwent an experimental cancer treatment which he found using China’s biggest internet search engine. Baidu’s Nasdaq-listed shares fell more than three per cent in morning trade on Monday following the move. Healthcare accounts for 20 to 30 per cent of the company’s search revenue, analysts at Nomura and Daiwa said, while search revenues represented some 84 per cent of web services firm’s total sales in 2015. The new rules mean the company must clean up in-search healthcare adverts and the positioning of paid-for search adverts of any kind cannot only be based on the highest bidder, said a statement posted on website of Cyberspace Administration of China. The number of such adverts must also account for no more than 30 per cent of a page of search results, the statement said.