In the latest example, CBS MarketWatch started airing a commercial Monday that re-purposes American Airlines' upcoming TV ad campaign. To see the ad, consumers can click a large square beside articles on the MarketWatch site, which publishes financial news and information.
Other major Web publishers also are pushing formats that resemble offline ads. Microsoft last week started running full-page ads that imitate movie trailers, forcing visitors to view a 10-second promotion before a requested page is shown.
Web publishers are testing new ad formats almost weekly to attract traditional advertisers, which hold the purse strings for many ad-dependent sites. The latest experiments, which blend larger units with formats borrowed from print and television advertising, are geared toward making traditional advertisers more comfortable with an oft-maligned industry.
"We're going to see more ads that are moving toward the TV and broadcast mediums, and that will increase even more so as broadband increases," said Denise Garcia, research director at Gartner.
And broadband usage is climbing. The Federal Communications Commission last week reported that 7.1 million homes and businesses had high-speed connections last year, up 158 percent from the preceding year.
But such advertising may come at the price of alienating consumers. For example, "pop under" ads, which launch in a separate browser window when a visitor exits the page, have become popular on mainstream sites including Yahoo, CBS MarketWatch and The New York Times on the Web. A campaign by wireless camera company X10, which blanketed the Net with pop-under ads, prompted widespread consumer criticism and debate within the Web measurement industry.
"You're seeing all these crazy ad units because no one has completely cracked the formula for what works," said John Keck, media director for the interactive division of Foote Cone & Belding, which plans and places advertising for such clients as Compaq Computer, Taco Bell and Major League Baseball. "People are trying to figure out what the consumer will bear. They don't know yet."
The move toward larger, more mainstream formats runs parallel to industry research seeking to prove the Internet is valuable for branding products. The Interactive Advertising Bureau, Microsoft, DoubleClick and others have commissioned research that endorses bigger ad formats as a means of leaving an impression with consumers. The research seeks to woo traditional advertisers with a language they can understand and to help publishers tap a larger portion of marketing budgets.
"Web sites are trying to get at the larger budgets like TV and branding budgets, which are more expensive and normally reserved for ads that run on TV, radio and print," Gartner's Garcia said.
At the moment, the Internet largely attracts product placements similar to direct mail, which typically comprises no more than 10 percent of a traditional marketer's budget--"and that's being generous," she added.
With publishers under extreme pressure to meet sales expectations, experimentation in online advertising has taken off.
"Web sites are asking themselves, 'How do we get the quick-service restaurant and the package-goods folks onto the Web when everyone says that the banner is dead?'" said Foote Cone's Keck.
Earlier this year, CNET Networks, publisher of News.com, introduced the "messaging plus" unit, a large, index card-size ad that lets consumers interact with a product without leaving the page. Several online publishers including The New York Times, Salon.com and Yahoo followed suit with a similar format.
Other publishers have tested formats that push the boundaries between editorial and advertising. Variety.com ran an ad called the Shoshkeles that superimposed a promotional image over Web site content. Ask Jeeves altered its home page for three days to promote the video release of the movie "Cast Away."
But more publishers are selling formats that traditional advertisers can relate to from the offline world. Half-page promotions are appearing on Yahoo's Mail service that are similar to magazine and newspaper advertising. Los Angeles-based VideoBanner and Atlanta-based Eye Wonder have introduced ad units that can feature full-length movie clips or other video without a plug-in.
And on Monday, MarketWatch introduced "embedded commercial units," or large inset ads on content pages that, when clicked, run 30- or 60-second broadcasts. The San Francisco-based site said the units are the first to feature full-length TV spots.
"This technology allows our advertisers to run their existing television creative on our site without launching a separate media player or a new browser," Scot McLernon, vice president of sales at MarketWatch, said in a statement.
Viewers must have the latest version of RealNetworks' RealPlayer software to see the ads.
Foote Cone's Keck said he is testing a wide range of ad formats online for his clients, adding that bigger is better. He said that interactive formats are compelling to advertisers.
Many such ad units come at a higher price. Because they are often the sole ad on the Web page, publishers command top rates for reaching the consumer exclusively. They also make the argument that they must recoup revenues of additional ads not present on the page, which has been a standard.
Keck said that the units can garner rates two to three times higher than standard banners; they can cost between $40 or $50 per thousand appearances.
The question for media buyers such as Keck is how to measure the value of the Internet like traditional advertising.
"Now I'm trying to evaluate the Web based on branding," he said. "Does a half-page ad on the Web equal a TV spot? And what is the Internet equal to? I don't know."