Internet advertising sales soared 35 percent to $16.9 billion in the U.S. last year according to a study conducted by the Interactive Advertising Bureau noting figures from accounting firm PricewaterhouseCoopers LLP.

Fourth-quarter Internet ad spending reached a record $4.8 billion, a 33 percent gain, over the previous year the companies said this week.

“Interactive advertising revenues continue to show solid growth as advertisers and agencies recognize that it is a medium that can uniquely affect consumer behavior from product awareness, to purchase intent, to actual purchase and then brand loyalty,” said Randall Rothenberg, President and CEO of the IAB.

The Internet accounted for 5.9 percent of all U.S. ad spending, up from 4.7 percent in 2005.

Dollars moved toward types of advertising that companies can easily measure, the report shows.

Search based ads by companies such as Yahoo Inc. and Google Inc. continued to dominate online ad categories. It was the largest, accounting for about 40 percent of spending, or $6.8 billion. A year earlier, the category represented 41 percent, or $5.14 billion, of online ad spending, the survey said.

“We have every confidence that this growth trend will continue as marketers allocate more of their total marketing dollars to interactive and the industry delivers effective and innovative platforms for connecting with consumers,” Rothenberg added.

Online classified ads were among the fastest growing categories, rising 43 percent to $3.06 billion, compared to $2.13 billion in 2005.