The Yankee Group forecasts that the US online advertising market will hit $50 billion by 2011.

The research company anticipates rapid growth in the coming years because of continued increases in online audiences, development of new types of advertising and new publisher business models that facilitate the selling of ads.

The Internet currently accounts for 20% of US media consumption, yet advertisers are spending on average only 7.5% of their budgets online.

Yankee group expects this gap will close somewhat by 2011, when the Internet will account for 25% of media consumption and attract 15% of ad dollars.

"With Internet connectivity nearly ubiquitous, online advertising growth is inevitable," said Yankee Group senior analyst Daniel Taylor. "And yet the Internet is still a relatively new digital medium. Steady growth in online advertising will require publishers to invest extensively in new media and advertising product development."