Forrester says US online advertising to reach $26 billion by 2010. But that’s only half the story.

This week, Forrester Research released a major study of US online advertising, predicting that the market will reach $26 billion by 2010.  The press release is here and includes some key data points.

A particularly fascinating aspect of the survey is that almost half of marketers plan to decrease spending in traditional advertising channels like magazines, direct mail, and newspapers to fund an increase in online ad spending in 2005.

The study’s author - Forrester Research Principal Analyst Charlene Li - provides some additional interesting details in her blog. She says that this is not the return of “The Bubble,” and growth is about more than just search.

This growth is clearly coming because marketers are seeing results with many forms of online marketing and advertising. But what studies like this often lack are data on the tools and techniques to convert browsers into buyers.

When traditional advertising people think about Web marketing, they automatically think about “getting attention” through programs like search engine advertising, banner ads, and Flash movies. They naturally gravitate to what they already know: television. They focus on one-way TV-style ads on the Web. But the Web is not TV.

Most advertising people do a terrible job when people click an ad and visit the client site or landing page. For most ad people, it’s all about “generating traffic” with little time and attention spent on the most important part = sorting those valuable clicks into categories based on the problems they face and developing compelling Web content to keep them interested to the point where they are ready to buy or become a sales lead.