Zenith, the media buying arm of Cordiant, plans to update the site daily.
"It separates the wheat from the chaff," said Frank Harrison, Zenith's media information system director and creator of the site.
Right now, travel marketers are the most sophisticated users of the Internet and at least 80% of all sites originate in the U.S., he said.
"But that's changing rapidly," he said. "The balance is shifting gradually to outside the U.S., including the user base. And you will see a plethora of [new] non-U.S. sites."
He said the number of Web sites on the Internet has grown since January from 70,000 to more than 120,000.
To promote the new site, Zenith is mailing 8,000 colorful postcards this month to advertisers and media owners around the world. The pictures on the postcards have captions like "Cut through" under a Swiss army knife and "Focus in" superimposed on a pair of optometrist's glasses used for testing eyesight.
Access to the site is free for now, but Mr. Harrison hopes eventually to limit certain parts of the site to paying users or Zenith clients, even tailoring information to individual clients.
Besides advertising, the Zenith site also indexes and gives access to TV, radio and print media sites as well as information about Zenith Media including an e-mail link.