SAN FRANCISCO — What if the Web held a sex party and no one showed up?

That’s what could happen now that the agency governing the Internet address system all but approved the creation of a new red-light district on the Web. The problem is that some of the biggest names in online pornography prefer not to be in that neighborhood.

The Internet Corporation for Assigned Names and Numbers on Friday agreed to move forward on a long-standing proposal from a Florida company to create a specialized dot-xxx suffix for adult entertainment Web sites. But the plan upset much of the adult entertainment industry. It joined hands with religious groups in lobbying against it, arguing that the new domains would lead to regulation and marginalization.

The alliance ‘made for strange bedfellows, for sure,’ said Diane Duke, executive director of the Free Speech Coalition, a trade association representing more than 1,000 adult entertainment businesses. The company sponsoring the dot-xxx domain, the ICM Registry, said it had a vision of a red-light district in cyberspace that was a clean, well-lighted place, free of spam, viruses and credit card thieves. Content would be clearly labeled as adult and the whole neighborhood would be easy to block. […]