Online retail spending in the United States slowed in April, as consumers tightened their purse strings in the face of rising food and oil prices.

E-commerce rose 15% last month from the same period a year ago, when year-to-year spending rose 18%, ComScore reported on Friday. April 2008, however, was a rebound from March, when spending increased 9%.

"While the e-commerce growth rates in 2008 are softer than what we saw last year, it's encouraging that April's growth rate represented an increase from what was obviously a soft March for online consumer spending," ComScore chairman Gian Fulgoni said in a statement. "One hopes that April will emerge as the beginning of a turnaround in the consumer economy and that spending will continue to accelerate as we move through the year and as the impact of the government's economic stimulus tax rebate program begins to be felt."

For the first quarter of the year, online retail spending reached $32.8 billion, including auction fees and autos, but excluding event tickets, ComScore said. The U.S. Department of Commerce pegged spending for the quarter at $32.4 billion.

While online spending has hit a bump, Web marketing to lure consumers is speeding along. The U.S. advertising market is predicted to reach $50.3 billion in revenue by 2011, more than double the amount of last year.

Driving the growth over the next few years will be the increasing size of the audience, the development of new types of advertising, and the creation of new publisher business models that will help sell interactive ads, according to the Yankee Group.