A DoubleClick spokeswoman said within minutes the glitch was identified as a small bug in the ad-server code, and over the next hour and a half, engineers deployed another bug to fix the coding.

As a result, delivery of banner ads, online promotions and click-through rates across the many Web sites across the U.S. were disrupted for about an hour and half on Friday. The company said it was contained to domestic ads.

In an e-mail to their customers, DoubleClick's Vice President of operations Bob Linsky said the company had to install a software patch to fix an unspecified problem "that was cascading through our ad servers."

The DoubleClick spokeswoman emphasized that customers where immediately notified of the problem, and that DoubleClick was quick to respond to the problem.

On Friday, Web surfers looking at DoubleClick-served banner ads saw an error message linked to a DoubleClick web address. As a result, companies using the ad service generated impressions but didn't get any click-throughs.