The death of numerous dotcoms and the consolidation among the survivors have concentrated the most popular Web destinations into fewer hands.
In North America, home to the world's largest Internet audience, just four companies control the sites that get half the Web traffic.
Steve Yap, communications director with Interactive Audience Measurement Asia (iamasia), said the trend had spread to the mainland, where the three leading portals - Sina.com, Sohu.com and Netease.com - accounted for 32.5 per cent of the time people spent on the Web.
'The landscape is dominated by a few major players. Sites controlled by the big three players were visited by 72.5 per cent of all home Internet users in urban China during March,' he said.
In Hong Kong, iamasia found that the sites controlled by five organisations - Yahoo!, Microsoft, Pacific Century CyberWork, the Hong Kong University of Science and Technology and Next Media - were visited by 91 per cent of the home Internet users, accounting for 27 per cent of the time people spent online.
In the United States, the concentration is even more pronounced.
According to research house Jupiter Media Metrix, four companies - AOL Time Warner (32 per cent), Microsoft (7.5 per cent), Yahoo! (7.2 per cent) and Napster (3.6 per cent) - account for half of the 72 billion minutes Americans will spend online this year.