The Sensex at the Bombay Stock Exchange, which had opened 40points lower this morning soon rebounded to cross the 20,000 mark in early trade today. But the benchmark index then again lost ground, to stand 95 points, or 0.5 per cent in the red, at 19,898, in afternoon deals, amid volatile trade, a short while ago. The market weakness was due to profit-booking, after four days of an uptrend, in which the Sensex had gained over 700 points. But stock markets in Japan, Hong Kong, Indonesia, Singapore, South Korea and Taiwan were up by between 0.1 per cent and 0.5 per cent.