Tim Armstrong, Google's advertising sales vice president, said in an interview before the Reuters Media and Advertising Summit that 2005 marked the turning point when advertisers switched from testing to investing in the decade-old medium.

"There is robust interest in online advertising and that interest is now turning into real dollars," Armstrong said, noting that market analysts are predicting a banner 2005 year with forecasts ranging from $10 billion to $15 billion.

"The experimenting and testing phase begun in the 1990s has ended. Corporate ad buyers are investing now," he said.

Jupiter Research estimates the U.S. online advertising market will grow 28 percent over last year, to $11.9 billion in 2005, moving to $13.6 billion in 2006 and $15.1 billion in 2007.

By contrast, Google, which dominates the fast-growing market for keyword-search advertising, has been growing at three times the industry rate, or around 100 percent a year.

Industry estimates put Google's market share at 30 percent of overall online ad spending, with as much as 40 percent of the category it dominates--paid search.

Get the full story at CNET News.com