Arlington, Va.—Advertising expenditures on newspaper Web sites rose 21% to $773 million in the third quarter compared with the same period last year, according to preliminary estimates released Tuesday by the Newspaper Association of America. The increase marked the 14th consecutive quarter of double-digit growth since NAA started reporting online ad spending in 2004. Newspaper Web site advertising now accounts for 7% of total newspaper ad spending, compared with 5.4% in the third quarter last year. Total advertising expenditures at newspaper companies were $10.9 billion in the third quarter, a 7% decrease from the same period a year earlier. Spending for print ads in newspapers totaled $10.1 billion, down 9% from a year earlier.