Online ad spending totaled $6.4 billion in Q4 2009, reports Clickz.com.

Despite being down for the majority of 2008, online ad spending saw a significant comeback in the last quarter of 2009. According to the survey conducted by the Interactive Advertising Bureau (IAB) and PricewaterhouseCoopers, advertisers spent 14 percent more on online advertising than they did in Q3, and spending was also up 2.6 percent over Q4 2008.

The survey also indicated that search engine optimization (SEO) continues to be important. Search marketing was the main avenue of online advertising, accounting for $10.7 billion in 2009, 47 percent of all online ad spending. Advertisers spent $2.9 million on search marketing in the last quarter of 2009, up 4 percent from the same period in 2008. Display ads were also up, making up 35 percent of the industry’s revenues.

The upward trend represented by the survey has many advertisers cautiously optimistic about ad spending in 2010.

A recent report from Econsultancy.com predicts that online advertising will increase 14 percent to $16.6 billion in 2010. Most marketers indicated that they would be spending a majority of their budget on search engine optimization (SEO).