Advertising spending for U.S. newspaper Web sites increased 18.8 percent to 3.2 billion in 2007, according to preliminary estimates from the Newspaper Association of America.

Spending on newspaper Web sites has now grown to account for 7.5 percent of all newspaper ad spending last year, an increase from 5.7 percent in 2006.

For last year’s fourth quarter, advertising spending on newspaper Web sites rose by 13.6 percent to $847 million compared to the same period a year ago. It was the thirteenth consecutive quarter of double-digit growth for online newspaper advertising since the NAA started reporting online ad spending in 2004.

“Even with the near-term challenges posed to print media by a more fragmented information environment and the economic headwinds facing all advertising media, newspaper publishers are continuing to drive strong revenue growth from their increasingly robust Web platforms,” NAA President and CEO John F. Sturm said.

Advertising expenditures at newspapers and their Web sites totaled $12.6 billion for the fourth quarter of 2007, while spending for print ads in newspapers totaled $11.7 billion. That compared with total advertising expenditures of $14 billion and print ad spending of 13.2 billion in the fourth quarter of 2006.