Jupiter, which has a staff of roughly 60 in Europe, declined to discuss potential layoffs. Its research group will be unaffected by the transaction, although a source said it remains up for sale as the company looks for much-needed funds to stay afloat.

With the deal, NetRatings supplants Jupiter to become the primary Web measurement firm in Europe.

Media companies and advertising agencies had used Jupiter's measurement data to determine on which Web sites companies should advertise.

But with the downturn in the global economy and subsequent slump in advertising and technology spending, fewer firms are paying for the data, depriving Jupiter of its primary revenue stream.

Jupiter recently disclosed in a U.S. Securities and Exchange Commission filing that its cash reserve would dry up completely in the middle of the second quarter unless it sold off assets.

eRatings.com purchase

NetRatings, 64 percent-owned by Dutch publisher VNU, also bought the 80.1 percent stake it did not already own in Internet measurement venture ACNielsen eRatings.com.

It paid $9.6 million in stock to AC Nielsen, another VNU company best known for its market research and TV audience measurement in the U.S.

VNU said it would continue to own a majority of the NetRatings shares outstanding.

NetRatings said the acquisitions will help it become the dominant Internet audience measurement service in North America, Europe and Asia.

The companies also said that they had settled Jupiter's pending patent infringement case against NetRatings.

NetRatings will pay Jupiter $15 million for a non-exclusive license to use its computer-tracking technology in the U.S. through June, 2005.

A merger between NetRatings and Jupiter fell through earlier this year, forcing the loss-making Jupiter to put its assets up for sale.

Last month, Jupiter sold NetRatings its ad measurement business for $8.5 million.

At 1625 GMT, Jupiter shares were trading at 18 cents, up 38.5 percent. Net Rating shares were up 1.6 percent at $12.02.