More than two dozen companies in China are postponing initial public offerings and security companies are pledging more than $19 billion for a fund to stabilize the countrys free-falling stock market. The 28 companies, which had obtained permission from Chinas securities watchdog for IPOs planned in Shanghai and Shenzhen, said they would postpone them due to recent market fluctuations and refund money already paid, the official Xinhua News agency announced late Saturday.