The study examined 15 e-commerce sites, including those of Martha Stewart, L.L. Bean and Office Depot. The study found that sites met an average of 49 percent of the usability guidelines developed by Nielsen's consulting company, the Nielsen Norman Group.
In a similar study performed by the Nielsen Norman Group two years ago, e-commerce sites met an average of 45 percent of the group's usability guidelines.
"If we continue at this rate for the next 15 years, we will reach a level that we really want to be at," Nielsen said. "Fifteen years is a long time to wait to get good services on the Internet, but in the big picture, this is a new technology, and whenever anything else was invented, it took a while to get it right."
Online shopping sites have long tinkered with their designs to try to optimize sales. E-commerce giants eBay and Amazon.com, for instance, have both overhauled their home page designs in the last two years in an effort to promote different parts of their site and highlight particular products.
Despite the design changes, e-commerce companies still face the problem of nervous shoppers. Only 46 percent of U.S. Net users bought something online in 2001, according to Jupiter Media Metrix. Meanwhile, U.S. consumers abandoned 66 percent of their shopping carts in 2001 before checking out, according to Forrester Research. And consumers who get irritated by an e-commerce site often don't return.
While some of this is attributable to security concerns or the desire to see a product in person, consumers can also be frustrated by Web sites that make products difficult to find or make checking out confusing.
"Usability has to be there at every step," Nielsen said. "If one step has a big problem, you've lost the entire order and people will go elsewhere."
Nielsen Norman Group has put together a list of some 207 usability guidelines. The guidelines cover everything from whether a site's product search engine will tolerate misspellings to whether a site requires a customer to select the state in the United States that they live in, something international users can't do.
Among the sites the study considered this year, L.L. Bean's scored highest by meeting 66 percent of the guidelines. Meanwhile, Home & Garden had the lowest score, meeting just 38 percent of the guidelines.
L.L. Bean did well by providing simple product pages and by doing a good job of describing different product variations, Nielsen said.
"As a mail order company, L.L. Bean has always had to emphasize giving people exactly what they need or else they wouldn't get any orders," he said. "They've just taken that to the Net."
Nielsen's study this year did not examine Amazon.com, which is considered by many to be one of the easiest e-commerce sites to use and which Nielsen rated No. 1 in his survey of e-commerce sites two years ago. In designing the survey this year, Nielsen had planned to compare all of the sites he looked at in the previous survey. However, many of those sites have since folded, so Nielsen chose to look at a completely new group of sites.