The Taiwan stock exchange index, which fell more than 21% last year, continued its free fall yesterday, shedding an additional 266 points to close at 6,152.43 -- the lowest level since August 1996, analysts said. The market was closed Monday.

With several major electronics companies expected to lower their earnings forecasts for the year, investors are increasingly jittery about the future prospects despite government moves to support the market, the analysts added.

Acer Inc., the core PC-making parent company of The Acer Group, closed yesterday's trading at $1.10, down $0.06 for the day.

On Dec. 23, Acer for the second time in 1998 lowered its forecast for the full year's profit after tax, from $108 million down to $77 million, despite raising its revenue forecast to $2.96 billion up from the previous $2.8 billion.

The company blamed the decrease in profits on a range of factors, including lower-than-expected profits from its global PC business and losses at its semiconductor subsidiary and in North American markets.

Other major Taiwanese PC and motherboard makers also saw their stock prices fall yesterday.

• Mitac International Corp., which counts Compaq Computer Corp. as its biggest customer, ended the day at $1.43, down $0.06.

• Asustek Computer Inc., one of the world's largest motherboard makers, dropped $0.24 to $9.11.

• The island's semiconductor makers were also hit by the slide, with Taiwan Semiconductor Manufacturing Co. Ltd. shedding $0.09 to end the day's trading at $2.11.

• United Microelectronics Corp., Taiwan's second-largest chip maker, fell by $0.04 to $1.21.