After years of double-digit percentage growth for internet advertising, this was the year when the medium finally took a hit right along with the rest of the media economy, seeing spending decline for the first time since the dot.com bust of 2001.

But unlike most other media, the web is poised for a comeback in 2010.

In its most recent forecast, eMarketer predicts that U.S. online advertising will decline 4.6 percent this year, to $22.4 billion, after increasing 10.6 percent in 2008. It marks the first year-to-year decline since 2002.

But the online research firm predicts that spending will rise 5.5 percent next year, to $23.6 billion. While that's well under the huge year-to-year increases the web posted after the dot.com boom, it's still more robust than any other media, many of which will remain in the red next year.

Search marketing will continue to drive the medium, drawing off the largest share of spending, but advertisers are also increasingly experimenting with video and social media.

Why the rebound?

Advertisers put off by the high cost of traditional media are turning to internet to achieve the same reach while spending less.

Also working in the web's favor is that unlike newspapers, magazines or radio, usage has shot up over recent years, allowing advertisers to reach mass audiences that were once only available through radio and television.

Another big factor driving the increase in spending is the internet's accountability. It's long been a major draw for advertisers, and it's become even more so as the quality of data has improved.

"Reliable data has become more and more available over the past several years," says Amiad Solomon, chief executive officer of Peer39, an online advertising technology company. "We see the marketplace becoming more sophisticated in how it can be used to sell advertising.

"Video only took off when broadband connections enabled a smooth user experience in viewing the video. After fast internet became the standard, suddenly video was everywhere. We see the same with data. The more data that can be collected, without traversing privacy standards, the better for all parts of the online advertising ecosystem."

Yet another draw is the internet's targetability, which has also increased in sophistication. With money tight, clients want to pay to target only those people who will respond to their message. "Advertisers can leverage data to reach their audience at a very granular level with specific messages," notes Solomon.

At the same time, new media isn't so new anymore. Whereas advertisers were reluctant to invest in the web during the last recession, many of them have gotten very comfortable with it since.

Local internet in particular has seen a huge boom in spending, a boom that is finally tapering off and will continue to flatten over the next few years. Next year local web spending will increase just 5 percent, compared to jumps of 50 percent four of the previous five years, according to Borrell Associates.

The economy has a small part to do with it, but mostly the slowdown is due to other factors.

"Many advertisers are beginning to shift back to some form of traditional media that once worked for them. They’re merely adjusting the dials to find the appropriate mix," Gordon Borrell told Media Life earlier this year.

Finally, web advertising will be boosted by the medium's increasing ubiquity. These days people don't just use the web to gather information.

They also use it for entertainment--Nielsen says that online users spent an average 200 minutes per month in November watching online video--and to keep in touch. That means ever-more time to absorb advertisers' messages.

Little wonder, then, that 72 percent of senior advertising, marketing and media people surveyed by Round2 this month said they plan to increase digital media spending next year, with half of them pointing to online's superior ROI compared to traditional media.

Still, it will be a long ways till online overtakes television for the top ad medium, despite its growth. Last year the web had a 13.8 percent market share to TV's 43.4 percent.