BEWARE OF GREGORY from Oakland. He is not single. Rather, he is married, and cheats on his wife Saturday nights before church, no less. Not only that, but "he dyes his hair and lies about his age," according to a post by his anonymous ex-girlfriend on Dontdatehimgirl.com.

Michael of Fremont? His former girlfriend reports his bad temper, sexual deviance and marijuana addiction on the same Web site. "Don't fall for his tricks because he will try and steal you blind," she writes. "Ladies, if you see this one coming, run the other way!"

And Jerome, the clubber from San Jose? He is a walking STD, says a recent caller on the local radio station 94.9 FM's nightly segment "Do Not Date."

Uncovering a potential partner's lies or bad behaviors isn't easy, especially in the online dating world, where well-written profiles or suave photos are hardly guarantees of a good heart and a clean record.

But the Web in particular is stepping up with free sites such as Dontdatehimgirl.com, Truedater.com and Manhaters.com to out the liars, marrieds and those who fib about their age, height or weight.

"There's a thin line between putting your best foot forward and not being truthful," says Tasha Cunningham, founder of the Miami-based Dontdatehimgirl.com. "I think it's the biggest dilemma the online dating world faces."

Cunningham started the company in 2005 after dating a man for almost five months who was in the process of getting a separation. He failed to share that with Cunningham. The site claims 1 million members and receives 400,000 hits a day. Cunningham estimates that women have entered information on 30,000 men.

While the site is for women, 20 percent of members are male and join to participate in the He Said She Said forum. Members of the site post the full name, city and photograph of the creep they say wronged them, along with an at times detailed description of exactly what said creep did.

"It's the MySpace of dating and relationships, for women," Cunningham explains. She even hears from women who've used True.com, which charges daters a premium membership fee to screen for married and felons.

On Dontdatehimgirl.com, women considering an online date or just curious Web surfers can read about men by plugging the men's names into a search engine. They can e-mail the author directly for more details. And yes, men who disagree with what's written can submit rebuttals. Male focus groups axed Cunningham's idea for Dontdateherman.com, a similar concept for men to avoid female liars, but Greatguystodate.com will be up by June 1.

"It's wonderful men who nominate themselves or are nominated by the women in their lives," she says.

There is a halo over the "W" in Womansavers.com, also known as Manhaters.com. On this site, women fill out questionnaires about a man's ego, trust issues and other datable qualities. A rating from zero to 122 is issued, and the average is a 23.

Choose a longer questionnaire and answer questions with "this man is a complete slob who you have to pick up after" or "in the early stages, he's really great, but once he has you hooked, all the relationship effort falls on your shoulders."

Naturally, the Web sites have outraged men, both the cads and the innocent ones. They argue that the profiles are embarrassing, damaging or false, and that it's unfair that the women remain anonymous while the men are fully disclosed. Many have demanded they be removed from the sites.

But in the case of Donthatehimgirl.com, the reviews don't budge. The person who makes the post can remove it anytime, Cunningham explains.

Some men have pursued legal action, with no success.

"The soap box is not liable for what the speaker says," explains Kurt Opsahl, an attorney with the Electronic Frontier Foundation, citing Section 230 of the Communications Decency Act. Passed in 1996, it protects Web site owners from content posted by third parties.

The speaker, however, still remains liable. Even an anonymous defamer can be tracked down through his or her IP address, Opsahl says.

Aptly named, Truedater.com exposes the good and bad apples -- of both sexes. 

Log on and plug in the member name or profile number of your potential date from one of the dating sites. The site works with 95 percent of them, from Match.com to Jdate.com and prides itself on sticking to the stats: Is she really 5 feet 10 inches with a glistening mop of golden locks? Is that photo of him from this decade?

"We don't want any personal attacks," says Jamie Diamond, a representative for Truedater.com. "If someone goes off on someone we're not interested in that. We also don't want to be Judge Judy."

As such, Truedater.com edits reviews. And, for every outing of a not-so-honest profile, there's a positive review about someone, like "She's a great girl and as cute as her picture. We just didn't have any chemistry."

"I like Truedater because it really focuses on the facts," says Meredith Macaualy, who moved to Portland, Ore., from San Francisco last month and uses the site to check out people from Nerve.com.

Her ex-boyfriend wrote a positive review about her on Truedater.com. And when she came across an unclear picture and even more unclear career description on another fellow's profile, she ran him through the site.

"It made me feel a lot more comfortable going on a date with him because there was nothing objectionable on the review," Macaualy says.

In some cases, you're losing way more than 30 minutes at Starbucks when you go on a botched online date, Diamond says.

"Some people fly across the country to meet people, and if you don't recognize the person picking you up at the airport, it can be really disconcerting," he says.

All this disappointment has fueled a culture of venting, from the therapist's chair to the radio waves.

Joe Breezy, host of 94.9 FM's "Do Not Date" show, says listeners call in sometimes seconds after unearthing a cheater. He averages 100 calls a night, and about 70 percent of callers are female.

"People have told me they listen every night to make sure the person they're dating's not mentioned," the disc jockey says.

It's enough to seek professional help.

Walnut Creek therapist Denny Reynolds says that while these sites are a "cheap way to get back at somebody," it's equally wonderful to have a place to go if someone is deceitful and hurtful.

When it comes to online dating, Reynolds tells her clients three things: Meet up right away. Use your intuition. And above all, be real.

"When you're out for revenge," she says, "it never feels good inside."

Jessica Yadegaran is a lifestyle writer for the Times. Reach her at jyadegaran@cctimes.com or 925-943-8155.

dating credit reports

Want a behavioral background check on your date before going out? These Web sites can help:

  • Dontdatehimgirl.com: Considered the FBI's most-wanted list of such sites, women post names and photographs of cheaters, marrieds, or tell tales of how they feel they were wronged. Rebuttals are common, and a forum allows users to e-mail each other for further details.

  • Womensavers.com: Also known as Manhaters.com, women research and rate before they date by filling out a questionnaire that produces a rating for men from slime to saint. Includes warning signs of cheaters, liars and abusers.

  • Truedater.com: Users, both men and women, post the nickname or profile number of the person in question and comment on the veracity of their profile, outing lies about everything from height and weight to age and marital status. Extraneous comments are edited.

  • True.com: A dating site that charges a larger membership fee to run felony and marriage background checks on its members. Still, users of the other sites have posted reviews about True.com members who were married.

    -- Jessica Yadegaran