In some ways, the most difficult connection on the Internet may be the very last one: between the computer screen and the human mind. Although finicky servers and overloaded phone lines cause their share of problems, the bits usually get delivered. The message, however, often doesn’t. It remains imprisoned within a confusing, indecipherable Web page. Viewers of the page follow wrong links. They can’t find what they want. They get lost, or they get bored–and they move on.

The hypertext markup language (HTML) used to create Web sites was created less than a decade ago. And as with any language, people learning it must babble for a while before they achieve eloquence. In the meantime, users of the Web struggle to decipher its mangled metaphors and broken syntax.

Jakob Nielsen has made it his business to watch people engaged in that struggle. Nielsen is a distinguished engineer at Sun Microsystems, the computer company known best for its high-powered Internet servers and its creation of the Java programming language. His observations, carried out in Sun’s usability labs in Menlo Park, Calif., are teaching Nielsen and his colleagues the rules of effective communication on the Web (see sidebar: “Jakob Nielsen’s Seven Deadly Sins of Web Design”). Nielsen shares those lessons in a biweekly Web column, “Alertbox,” which is considered a must-read among usability engineers (www.useit.com/alertbox/). His latest book, Designing Excellent Websites: Secrets of an Information Architect, is due out this month.

Nielsen also travels widely, relentlessly advocating the cause of the beleaguered Web user. William Allstetter caught up with Sun’s usability guru recently at the Human Factors & the Web Conference at the AT&T Learning Center in Basking Ridge, N.J.

TR: What are the defining characteristics of an unusable interface?
NIELSEN: It’s difficult to learn. You get low performance even if you are an expert. You hate it. You make lots of errors. And you can’t remember how to use it after you have been on vacation.

TR: And you think a lot of Web sites fit that description?
NIELSEN: Yes. The default on the Web is that people cannot use it. Jared Spool, founder of User Interface Engineering (www.world.std.com/~uieweb/) and an expert on interactive design, did an interesting study. He showed people a home page and asked them to find a specific piece of information that he knew existed on that Web site. But users succeeded in this task only 42 percent of the time.

TR: Why does the Web present such difficulties?
NIELSEN: I think the reason is that it is designed by people who don’t understand interactive design. Most Web sites have never been tested on real users. Often, the only test is taking somebody into the art director’s office to look at the screen. And that somebody is typically a vice president of marketing, who is thoroughly familiar with the company and so of course can understand the site design perfectly. But this is not a person who represents the general Web population.