Until recently, I had never been to MySpace or Facebook. Even though I'm not yet 30, I had the feeling that I had missed that trend, that I was just a year or two behind the curve.

But when I read in BusinessWeek that the number of people 35 and over visiting Facebook had doubled in June from the year before, I decided I had to give it a try.

I'm glad I did. I learned that social networking online doesn't have to be the scary province of teens and college students. It is a little intimidating to enter a world where the rules and etiquette aren't clear — and I think I've already committed my share of faux pas — but it's also exciting.

It's not hard to see why Facebook has garnered 31 million active users in just over three years. A more polished alternative to the anything-goes MySpace, the site connects long-lost friends and new acquaintances.

For those who worry about privacy, Facebook requires participants to use their real names and has pretty strict safeguards that users have the option of making even tighter.

But let me back up. Social networking sites allow people to create personal profiles, like mini-Web pages, and use them as a platform for making connections with other people on the site.

Facebook's site, www.facebook.com, is intriguing from the get-go. A nifty feature, "Find your Friends," makes it very easy to see who you might know who is already registered on the site; just type in your e-mail address and password (multiple ones, if you've got them), and the program will spit out every contact in your address book who is also on Facebook.

When I saw that dozens of my high school and college friends and some co-workers from my first job were on Facebook, I had to join. That's what the site's creators are counting on.

After you join, it's easy to set up a profile and customize it. Just answer as many questions as you want out of a multi-step questionnaire. Upload a picture, and the basic profile is finished.

One of the site's main features is the "news feed," a running list of users' activities. When one of them befriends someone else, adds an application or changes part of his or her profile, it shows up on my feed. So when my Australian friend removed "single" from her relationship status, I noticed.

Adults looking to network with their contemporaries might want to consider Eons, a 50-plus social networking site that has attracted 560,000 profiles in the past year. The site (www.eons.com) offers plenty of technical assistance, as well as health and lifestyle information.

It might be harder to find existing friends on Eons, a relative newcomer to the Web, than on one of the more mainstream social networking sites.

A final warning: These sites can be addictive. I might lose interest once I stop finding old friends to reconnect with, but with more people joining each day, I doubt that will happen anytime soon.

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