online advertising began in 1994 when hotwired sold the first banner ads to several advertisers. revenue in the united states grew to an estimated $7.1 billion in 2001 or about 3.1 percent of overall advertising spending. the dot-com bust destroyed or weakened many of the early online advertising industry players and reduced the demand for online advertising and related services.
The industry regained momentum by 2004 as the business model for "Web 2.0" came together. A number of businesses emerged that facilitated the buying and selling of advertising space on web pages. Entities that operated web portals settled on the traditional "free-tv" model: generate traffic by giving away the content and sell that traffic to advertisers. Most web sites, with the exception of transaction ones such as eBay, generate the preponderance of their revenues from the sale of advertising inventory—the eyeballs that view space allocated for promotions—to advertisers. In the first half of 2007 alone, advertisers in the US spent more than $10 billion advertising on websites. That was about 14 percent of all advertising spending.