The secret to making easy money on the World Wide Web is as clear as the bright red neon signs in Times Square: sex sells. Just ask Seattle housewife turned Web entrepreneur Beth Mansfield.

"I feel like I've won the lottery," said Mansfield, whose online index of pornographic Web sites will generate $1 million in advertising next year. "I guess I was at the right place at the right time."

For three years, pundits, colossal corporations and Ivy League entrepreneurs have crunched numbers, espoused theories and issued white papers in the quest to cash in on the Web.

Far below the ivory towers, though, in the seedy corners where intellects dare not wander, entrepreneurs are selling bawdy, fetishist, keep-the-kids-away-from-the-monitor sex.

And they are making a killing.

Entrepreneurs of eroticism are reportedly earning millions in subscription fees and advertising. They are making a mockery of conventional wisdom that says the Internet is not yet a viable commercial medium.

Equally compelling is who is making the money. In ad industry long dominated by males, there are now some formidable female players, including housewives and former strippers who have learned enough HTML coding language to put flesh on the Web.

Mansfield, who created Persian Kitty's Adult Links - an index that is the Yahoo! of porn sites - earns $80,000 a month in advertising. A former Los Angeles dancer and bit movie player now runs a $2 million-a-year Web site called Danni's Hard Drive.

And there is Janey Huntington, a 45-year-old grandmother who began putting pictures of herself on the Web last March. The site now features amateur models from across the world. It has 10,000 "hits" a day and generates $10,000 a month in advertising.

These women do not look at pornography as a source of exploitation of women but as a source of income. "My husband resigned last year from his position as vice president of information services at a major company," said Huntington. "Now we do this full time."

This profitable coupling of the oldest profession and the spiffiest new technology is not that surprising. The same thing happened in the early 1980's with the VCR, which the mainstream film industry fared would result in fewer people going to movie theaters but pornographers embraced as a new vehicle for delivering their product. Pornographic videotapes, particularly those produced by Playboy, have consistently ranked among the top rentals.

Indeed, pornography has historically helped drive other consumer technology, such as video on demand in hotel rooms. And in the case of the Internet, some of the most cutting edge ventures involve porn, including sites that offer live sex, direct from Holland, for upwards of $4 a minute.

Another site offers live sex video sessions with popular porn stars and strippers. The site permits users to direct the sessions or the performers by typing or speaking commands into the computer.

Of course, the adult sites are not popular only because they are selling sex. What they are really selling is anonymity.

Until a few years ago, buying porn meant driving to the other side of the tracks, where you risked being seen toting a little brown bag full of smut. Interactive porn meant hanging out at a strip-club.

In the words of Greg Wester, research director for the Boston-based Yankee Group: "You don't need sunglasses and a trench coat when you're surfing the Internet."

With the Internet, the smut is delivered to your desktop. And a user can easily turn off the computer - and the offensive content - if the viewing is interrupted by a significant other, or boss.

Critics like to point out that a disproportionate share of the content on the Internet is pornography, but what is more striking is its disproportionate popularity, according to Bob Brownstein, director of western sales for New York-based PC-Meter.

Of the top 20 most popular stops on the Internet (as measured by PC-Meter) two are adult sites, and they are the only ones in the group that charge people to visit. OF the top 500 site that get 1 percent or more of visitors, 50 are adult sites.

Put it this way: the "Cyberotica" site ranks as the 14th most popular, one slot above www.disney.com.

"The (adult sites) are outdrawing some of the real, established entertainment sites," said Brownstein.

This traffic translates into dollars in one of two ways. Either visitors pay for subscriptions, or advertisers pay to attract the passers-by. The advertisers are mostly other adult sites that want to sell subscriptions or pornographic merchandise. Cyberotica, for instance, gets a reported 300,000 individual hits a day.

Club Love, which is among the four most popular adult sites, has 50,000 members who pay $10 a month for access. Along with sales from other sites, it is earning $1 million a month in revenue, according to Seth Warshavsky, president of Internet Entertainment Group, the parent company of Club love.

A portion of the income comes from Club Love's round-the-clock live sex video conferencing. The service costs $39.95 for 15 minutes and includes live footage of strippers, and even pornography stars performing various acts. He said it's among the most advanced uses of technology on the Internet, but it's only going to get more advanced - thanks in part to pornography.

"Within the next six months, you'll see near television quality over the Internet," he said.

Despite his success, Warshavsky said, "it is not easy to make money on the Internet." He said his company initially invested $2.5 million in technology and infrastructure. He said that until recently, he was also spending $150,000 a month on advertising.

It is not just big operations, though, that are making money. And the entrepreneurs are not budding Larry Ellisons, the chairman of Oracle Corp., but Larry Flynts. They don't have curricula vitae - or even resumes - but they often bring life experiences and a sense of what people really want to see.

The potential for mercurial success - and a typical business model - is exemplified by Ashe, a former stripper, who is making a small mint on the Internet.

Ashe runs the Web site "Danni's Hard Drive," which features pictures she has licensed from magazines called "Score" and "Naughty Neighbors." The site registers 3.5 million hits a day and Ashe sells subscriptions to a portion of the visitors for $9.95.

Ashe's company made $1 million last year and will make double that this year, she said. The number of employees has grown from two last year to nine, including a photographer who flies to Paris, Italy, San Francisco and New York to capture new models on film.

Ashe considers herself a serious businesswoman and approaches her Web site with the intensity of Bill Gates attacking Netscape.

Her theory is that you cannot just make money on the Internet by showing dirty pictures. She thinks the key is to focus on what makes the World Wide Web special - namely, Hyper Text Markup Language.

Ashe builds her Web pages so that every detail or image that might titillate a viewer is linked to some related site. "The whole purpose of hypertext is to not make this a linear experience," Ashe said. "It's meant to be highly personal... where people can lead themselves around."

Ashe's site also puts a fine point on the key to success for attracting new subscribers. It's known as the "heroin business model": The sites give away enough free pictures to get the audience salivating for more, then start charging.

The success of Ashe and others also disabuses the notion that people won't pay for goods and services over the Internet. It also puts a crimp in the argument that the reason Web commerce hasn't taken off is that people are unwilling to entrust their credit card numbers to Cyberspace.

"When a useful good or service arrives, people pony up," said Kate Delhagen, analyst with Forrester Research in Cambridge.

Delhagen said that most goods finding a market on the Web - pornography, books, CDs and commodity gifts - share two characteristics: they are low cost and they aren't personal.

Delhagen prophesies that, as was the case with VCR tapes, the popularity of pornography could pave the way for other products.

"People may start giving their credit card to an adult site, but it will transfer to other sector," she said. "It's what happened with VCRs: The guy in the house bought it to watch some dirty movies. Then eventually, someone else in the house said, 'Hey, I want to use the machine.' "

Unlike Ashe's company, others rely on advertising, not subscriptions.

Janey Huntington and her husband, Steph, earn between $8,000 and $10,000 a month in advertising from the "amateur" site. The site features topless pictures of Janey and pictures of friends and other amateur models from around the world.

Huntington and the other "models" post their e-mail addresses. She says she gets 100 to 150 e-mails every day and responds to all of them. She said only a handful are offensive or critical of her efforts.

Meanwhile, the uncrowned queen of adult Internet sites is Mansfield, the 35-year-old Seattle housewife who runs Persian Kitty's Adult Links. The site has no actual adult content, it just provides a directory of more than 1,000 adult sites.

Mansfield started the list in Oct. 1995 because she was "fascinated by the breadth of the Web and wanted to see how many people I could get in my corner," she said.

How many people? At least 260,000 a day, according to third-party evaluations. That has meant $80,000 a month in advertising from adult sites, and Mansfield expects to hit one million in revenue next year.

The promise of profits from the adult field also has lured some traditional mainstream companies, such as New Jersey-based Tiarra Corp.

Tiarra has done graphic designs since 1987 and Web page designs since February. Among Tiarra's 250 clients were such stalwarts as Gerber Corp.

But when the company realized how much money pornographic sites generated, it decided to jump in. It now has controlling interest in nine adult sites, which generate $30,000 a month in advertising, according to company founder Mark Tiarra.

Tiarra said that aside from pornography, it's tough to make a lot of money right now on the Web. No matter how much money they invest on the project.

"I just laugh when I hear that a corporation spends $3 million on their Web site. They're morons," Tiarra said.