"Older adults are the fastest growing demographic on the Internet," said Professor Vicki Hanson of the School of Computing at Scotland's University of Dundee on the opening day of a global World Wide Web conference in Madrid.
While just over one-fourth, or 26 percent, of 70-75 year olds went online in the United States in 2005, the proportion was 45 percent last year, according to data from the Pew Internet & American Life Project, she said.
The percentage of those aged 76 years and over who surf the Web rose during the same period from 17 percent to 27 percent.
Britain has experienced similar sharp gains in Internet use by people in this age group, said Andrew Arch of the World Wide Web Consortium (W3C), the main international standards organisation for the Web.
"They are basically doing the same things as everyone else. Using the Web for communication, then quickly moving to other activities like information seeking, online banking, shopping," said Arch who works to boost Web accessibility for older and disabled users.
Sending and receiving e-mail is the most popular online activity for Internet users age 64 and older, according to the Pew study.
But older Internet users are less likely than younger Web surfers to do online banking and shopping -- and far less likely to use social networking sites, it found.