About half of all online shoppers leave typical e-commerce sites without finding what they want even though the item is right there on the site all along. Web shoppers also abandon transactions before checking out more than 70% of the time, according to industry estimates.

The numbers can easily be improved, according to Jakob Nielsen, a leading authority on Web-site usability and principal of Nielsen Norman Group, a think tank covering the human use of technology. “E-commerce sites can as much as double sales volume by simply becoming easier for customers to use,” says Nielsen.

Usability refers to a Web site’s design and functionality. Measuring site usability shows companies how successful they are in enabling site visitors not only to accomplish their tasks but to do so in the most efficient way possible. A site with poor usability can have damaging effects that go beyond lost sales. Cluttered home pages, poorly organized information, confusing or complex navigation, slow-loading pages, and frustrating checkout processes are among the most common usability problems.

Meanwhile, a well-designed and easy-to-use Web site provides a better user experience and is more successful in converting site visitors to purchasers. It also provides a stronger opportunity to develop long-lasting and profitable relationships with online customers.

Highly usable sites share the following important characteristics:

Intuitive: Users can rely on common sense to navigate the site.

Simple: Web pages are straightforward and devoid of jargon and pointless graphics.

Fast: Pages download quickly, and streamlined registration and checkout processes allow customers to get in, take care of business, and get out.

Reassuring: Customers receive clear feedback on their intended actions that an order has been successfully placed or canceled, for example.

Consistent: Uniform presentations and patterns in page design and content structure make the site easy for customers to use.

Forgiving: Good sites are error-tolerant and allow customers to easily correct mistakes or access help.

Pleasing: These sites are visually interesting and attractive.