Several factors caused the rise and fall of satisfaction scores throughout the year, he said. As expected, satisfaction dropped during the holiday season -- largely because of an influx of first-time visitors, who are less familiar with any particular site, he said. As a result, that group of shoppers is harder to please.

"Further, the scores didn't completely rebound in the spring 2006 index for a very obvious reason: Consumers constantly are raising their expectations and demanding even higher levels of site performance and customer service from the industry's largest retail sites," Freed said. "As e-commerce continues to evolve, shoppers shape their expectations based on the collective experiences of all the sites they visit."

From the customer satisfaction perspective, large multichannel retailers on the Web often struggle to keep up with Web-only merchants and successful direct marketers. For instance, an analysis of browser satisfaction levels reveals:

Three of the top-performing companies are Web-only merchants, which is not at all surprising considering they can devote all resources to the Web and don't have the challenges of multichannel consistency.

Amazon.com is the only company that ranks in the top five for both sales (no. 1) and customer satisfaction (no. 2).