With over 25 million members, protected by the anonymity afforded by the website, the site is truly revolutionizing the way people cheat.

In picturesque Rambouillet, the conservative mayor asked a bus company to remove the ad on the grounds that it breached the civil code and threatened the sanctity of marriage.

An anti-Gleeden petition that was circulated on social media garnered more than 20,000 signatures, while a #stopgleeden hashtag proliferated on Twitter.“Fidelity is not for sale!

In an era of surveillance cameras, leaked emails and heavily publicized presidential affairs, sociologists said the desire by would-be cheaters to avoid getting caught by an irate spouse was helping to drive traffic toward extramarital dating websites, where the risk of detection was less perilous than seducing a neighbor.

The costs of infidelity were underlined here recently after the trial in February of Dominique Strauss-Kahn, the former head of the International Monetary Fund and onetime favorite to become president of France, whose penchant for sex parties helped destroy both his political career and his marriage.

Similarly, advocates of same-sex unions have been taken aback in recent years by the stronger-than-expected backlash against the legalization of same-sex marriage here, which prompted hundreds of thousands of protesters to take to the streets.

Olivier Ciappa, whose giant black-and-white photographs of same-sex celebrities in intimate poses have offended some people, said that while the world saw France as the home of seduction, the country was “much more reactionary than people like to think.”That conservative strain has provided the perfect foil for Gleeden and other extramarital websites that have sought to lure subscribers with controversial ads.

Another Gleeden campaign on the Paris metro suggested that taking a lover was less expensive for the national health service than taking antidepressants. “They should have thought of ”When the ads were introduced, several were removed by the police, the company said.

A campaign by Ashley Madison, another extramarital website, featured President François Hollande and his three predecessors with smudged lipstick on their faces. Gleeden, launched in 2009, has a million subscribers in France, and 2.4 million globally, who can anonymously trawl profiles for lovers.

President Hollande was targeted by the news media after he was discovered last year sneaking out of the Élysée Palace on his motorbike to meet his mistress, a French actress.

His scorned former girlfriend, Valérie Trierweiler, responded with a damaging tell-all book exposing how the affair had pushed her to binge on sleeping pills.

PARIS — In a country recently transfixed by the trial of a famous politician that revealed details of his orgy escapades, and where the president was found to be cheating on his live-in partner, an ad promoting extramarital affairs might not seem like such a big deal.