E-commerce vendors may face an obstacle bigger than effective advertising and security concerns: poor site performance.

Andersen Consulting discovered in a recent study that more than a quarter of all the purchases attempted over the Internet never go through. The firm went shopping at 100 of the most popular on-line stores. Of the 480 items it tried to purchase, it only succeeded in completing 350 transactions.

The study revealed many of the sites could not take an order, crashed in the process, were under construction, had blocked entry, or were otherwise inaccessible.

The Andersen study did not name the best and worst performers, but it did note that none of the tested sites were without glitches. However, the sites of electronic-only retailers performed better than their traditional store-based competition.

Another blemish on the face of on-line shopping is the flagging delivery times of ordered goods.

The study found traditional retailers delivered an order when promised only about 20 per cent of the time, while e-tailers managed a more respectable 80 per cent reliability.