NEW YORK - U.S. Internet advertising revenues grew more than 26 percent to about $10 billion in the first six months of the year, according to a study released Thursday.

Keyword ads — such as those displayed alongside search results at Google Inc. and other search engines — remain the most lucrative, accounting for about 40 percent of online revenues.

Display ads made up 21 percent of total revenue and classifieds had 17 percent. Other formats include video, e-mail and sponsorship ads.

The figures come from a PricewaterhouseCoopers LLP study conducted quarterly by the Interactive Advertising Bureau, an industry trade group.

Despite the growth, online ads remain a small part of overall advertising spending, although the Internet is widely expect to command more of the marketing dollars now going to television, print and other traditional media.