Page design sometimes gets the most attention. After all, with current web browsers, you see only one page at a time. The site itself is never explicitly represented on the screen. But from a usability perspective, site design is more challenging and usually also more important than page design.
Once users arrive at a page, they can usually figure out what to do there, if only they would take a little time (OK, users don't take the time to study pages carefully, which is why we also have many usability problems at the page level). But getting the user to the correct page in the first place is not easy.
In a study by Jared Spool and colleagues, when users were started out at the home page and given a simple problem to solve, they could find the correct page only 42 percent of the time. In a different study by Mark Hurst and myself, the success rate was even lower; only 26 percent of users were capable of accomplishing a slightly more difficult task which, in the case of our study, was to find a job opening and apply for it (averaged across six representative corporate sites with job listings).
The reason for the lower success rate in our study relative to Jared Spool's study was not because we had picked particularly poorly designed sites; on the contrary, we were looking at sites from fairly large and well-respected companies. The difference in success rates was due to differences in the task complexity. The 42 percent success rate was the average outcome across a range of tasks where users were asked to find the answers to specific questions on a website-in other words, the exact task the Web is best for. In contrast, the 26 percent success rate was the average when users had to carry out a sequence of steps in order to complete the task of finding and applying for a job. If a user was prevented from progressing through any one of the individual steps, then he or she would not be able to perform the task. After all, you can't apply for a job if you can't find it. But it also does you no good to find a job posting if the application form is too difficult.
The problem is that web usability suffers dramatically as soon as we take users off the home page and start them navigating or problem solving. The Web was designed as an environment for reading papers, and its usability has not improved in step with the ever-higher levels of complexity users are asked to cope with. Therefore, site design must be aimed at simplicity above all else, with as few distractions as possible and with a very clear information architecture and matching navigation tools.