YOU KEEP A-CLICKIN' BUT YOU CAN'T COME IN

So you thought the Internet was predominantly free to anyone with a computer and an Internet service provider? Guess again. There's a little-known trick by which a Web site can see where you're coming in from and decide whether you get in or whether you get hit with a dummy page aimed at keeping you out.

Call it a high-tech version of the ancient Studio 54 entry system if you will, but domain-name identification is coming into slowly increasing use. Insiders call it Web access blocking. And the Wall Street Journal says it's used for any purpose from trying to keep the competition from learning one company's developments to showing customized advertising to some but not other customers - and we're not even talking about membership-only sites, either, folks.

Oh, by the way - domain-name identification users can also send you somewhere else at will, the Journal says. If it sounds like a slightly more legitimate version of the kind of endless looping numerous fly-by-night porn sites are notorious for (and now under the Federal Trade Commission's watch-it crackdown), it's still a growing trend with mostly mixed reviews.

Nevertheless, the Journal says, it's a reminder that surfing the Internet is not always a strictly private affair. "(I)t's becoming more like wandering around a trade show with your name tag on," Junkbusters Corporation's Jason Catlett tells the Journal.

And don't think that only privacy advocates are skittish about the practice. The Journal says new Net companies watch who visits from where and how often surreptitiously, which tells them whom they should pursue for potential investors. They do it to size up potential acquisition targets and merger partners. And, again, they use it to try freezing out competition or audiences they just don't want.

What about governments possibly using the technique? The White House and other American government agencies gather the Web addresses of everyone who hits them online, saying it improves their Web pages and helps them get valuable intelligence against hackers.

But it works two ways, too, often enough. The Australian government left an unusually high number of "footprints" on one rather hot site - which just so happened to use a version of domain-name identification. And its owner wasn't shy about exposing the heavy hits. She's adult site owner Bernadette Taylor, whom The Journal says posted a long list of agencies whose Web addresses showed up in her logs.

Incidentally, among the first Web dwellers to use domain-name identification blocking were child pornographers, hate groups, and people selling stolen goods, the Journal says. They would look up digits used by government investigators and then program their Web sites to screen them out, creating a somewhat complicated cat-and-mouse game between themselves and the law.

And - the Journal swears on this one, ladies and gentlemen - the U.S. Internal Revenue Service says it has stopped its version of the practice because (we are not making this up) because it was concerned over unwarranted invasions of privacy.

The technique requires no elaborate education, just some simple codes familiar to Web administrators, the Journal says. Within as little as five minutes, then, a Web site can start blocking, steering, or misdirecting users it doesn't want hanging around.