For most companies, advertising is a diversified part of their business.  Most businesses don't just advertise in one place or in one medium.  A combination of online, offline, print, television, radio, and other forms of advertising usually make up the entire marketing portfolio for successful companies.

A report by comScore Networks, sponsored by Yahoo, and covered by Internet Retailer suggests that online advertising should be just as diversified to be successful.

The study compared page views, time spent at advertiser's sites, and conversion rates of over 1 million U.S. web surfers who were either exposed to search and displays ads together or separately.  The findings, which I'll highlight in a moment, overwhelmingly suggest that the best advertising approach for internet marketers is a combination of search and display ads.  Although search advertising may be all the rage these days, the recommendation of comScore validates a continued investment in display ads in addition to search ads.

Specifically, the study found:

• Users exposed to both types of ads increased their page views by 68% compared to the single-format viewers
• Users exposed to both types of ads spent 66% more time at advertiser's websites
• 244% more users who were exposed to both bought from advertisers online
• 89% more users who were exposed to both bought from advertisers offline
• Exposure to both ad formats increased searches for advertiser's products by 26%

The findings are pretty hard to argue with.  Granted, it's only one study.  But with a sample size of over 1 million people, those numbers are probably pretty close to accurate.  So before you pull all of your online advertising dollars out of one format and stick it in the other, roll 244% increases in purchases around in your head.

Think of it like a battlefield:  a split-front with two avenues of attack is usually more successful than a single, direct confrontation.