The current mean availability of FTSE 100 companies' Web sites equates to 99.53 per cent per annum - 41 hours of downtime, according to research by network management consultancy Parallel Ltd.
The findings, based on monitoring on-line performance over a three-month period, identifies that 13 per cent of the sites did not achieve 99 per cent availability. The Internet presence of one company - a large retailer with an on-line purchasing function - was off-line for 1.84 per cent over the period, the equivalent of almost 7 days per annum.
Retailers, who stand to gain the most from efficient websites, were among the poorest performers. On average the general retail sites surveyed were unavailable to customers for a total of three days per year.
"The denial of service attacks in 2001 on Yahoo, e-Bay and Amazon.com underline the importance of on-line performance," said Tim Moore, director, Parallel. "According to generally accepted analysis, the attacks collectively cost around billion in lost sales, damage to the brand, the need to upgrade systems and the direct impact on market capitalisation.
"Indeed, it is clear that the customer's experience of a company's Web site will increasingly have a direct impact on sales and brand reputation. The more so when you consider that many of the FTSE 100 companies now use the Web to automate key relationships with partners and suppliers."