The Sensex at the Bombay Stock Exchange opened 79 points, or 0.4 per cent lower, at 17,913, Friday morning, on selling by investors, after some disappointing quarterly results, and weak global markets. Remaining weak, the Sensex stood 66 points, or 0.4 per cent in the red, at 17,926 a shortwhile ago. Other Asian markets in Japan, China, Indonesia, Hong Kong, Singapore, Taiwan and South Korea were down by between 0.3 per cent and 1.3 per cent, after poor economic data from Japan.