Call it the graying of the internet.

In its youth, the web was the playground of young, tech-savvy folks. That certainly changed as the medium has become more mainstream, but just how far may come as a bit of a surprise.

In Britain, so-called silver surfers, users over 55, are now the second-largest group on the internet, behind only the 35-to-44-year-old age group, and within a short period, the next six to nine months, they are expected to become the largest in the UK.

"Now, because so many people have internet access at home, it is really changing the profile of who is active on the web," says Heather Hopkins, vice president of research at Hitwise in Britain, which has tracked the evolution.

Much of the silver surfer growth has come about in just the last year. The group accounted for 22 percent of all British internet visits in the four weeks to May 12, 2007, according to Hitwise, up 54 percent since the same period in 2005 and 40 percent since 2006.

Last year this rapid growth propelled the 55-plus age group past the 18-24 demographic, the No. 2 category. That leaves only 35-44s, which accounted for 23.5 percent of internet visits in the four weeks to May 12, 2007, and that margin is fast narrowing.

"What is happening online is much more representative of what’s happening offline. The usage patterns now reflect the offline population," says Hopkins. Government statistics show 18 percent of the British population is aged 65 or older.

Just how global this trend might be is hard to say, though generally the over-55 online population is gaining for the same reason: the mainstreaming of the medium.

In the U.S., that's very much the case. While silver surfers still make up the smallest online demographic based on share of internet usage, accounting for 16.2 percent of U.S. internet visits, that's up from 14.7 percent in 2006, according to Hitwise.

Less clear is whether they will ever become dominant. In the U.S., they make up a smaller share of the overall population, just 12 percent to the UK's 18 percent.

In tracking the UK's silver surfers, Hitwise found that their usage wasn't all that different from other demographics. The top categories visited by that age group are search engines as well as adult, shopping and classified sites. These are also the categories that rank among the most visited for the internet overall.

Where the silver surfers do tend to spend more time is on travel and news and media sites, likely because retirees, which account for many of the over-55s, have more time on their hands than other age groups.

The 55-plus demographic accounted for 26.7 percent of British internet visits to travel web sites in the four weeks to May 26, 2007. That was the largest share of any demographic. In fact, silver surfers made 21 percent more visits to travel web sites than the 35 to 44 year old demographic, according to Hitwise.

The story is similar for news and media sites. Silver surfers represented 24.5 percent of British internet visits to that category in the same time period. Again, they were the largest group to the category, making up to 6 percent more visits than 35-44s.