To visitors, the web site represents a context with its own constraints for taking actions and fulfilling goals. These constraints are different from the more general constraints of the genre context discussed in chapter 6 and the more specific factors of the page context covered in chapter 8. At the site level, there are seven key usability design issues that are particularly important for creating effective web site interfaces:

• Conceptualizing the site with a visitor-centered focus
• Positioning the content
• Speeding up the response time
• Smoothing the navigation
• Assuring reasonable confidence in site security and privacy
• Making the site visible
• Maintaining quality

These seven constraints supersede any human factor guidelines at the page level with which they conflict....

Positioning the Content

Content owners and authors are usually the domain experts. They should be members of the usability design team from the very start. Before the designer can create formats, layout, and pages, the content needs to be specified.

Specifying the goals: Defining a site's content starts with specifying goals. Making sure that the users' functional goals are met in the site design is paramount. The site's goals and functionality should be clearly marked and visible on the site's home page and on the most likely pages from which the site may be visited. This information can be effectively provided by using buttons or tabs with key words denoting the primary site functions....

Specifying the tasks: Task analysis to decide what tasks follow from the identified goals is the next step in the process of creating site content. Tasks can range from the general, such as "finding information," to the specific, such as "contact customer service." The designer should not only specify the tasks, but also prioritize them. Priority can be determined on the basis of the most to least important tasks or on the basis of a performance frequency scale. By prioritizing the tasks, the designer can decide on the order of functionality presentation on the site's home page and on the subsites. Furthermore, in defining tasks, the site's title should represent a major task and the site's topics should represent subtasks. Each topic should have a clearly stated goal. The subtasks should also be ordered according to which task is most likely to be performed. Defining the tasks and topics can be done by such methods as structured interviews and focus groups, which are discussed in chapter 12, Evaluating Web Usability.

Organizing site and content: The goal here is not simply to organize information on a single page, but to make the site's content coherent. A site that is structured in a coherent manner for the user is one that supports the user's structural and functional mental models of the content. These models should be directly related to the content's goals and tasks discussed earlier. Often a site's content is organized to reflect the internal structure of an organization (Heller and Rivers, 1996) instead of user expectations of the site's topics and tasks.

To ascertain the users' mental models of information organization (after specifying the tasks and topics as described earlier), we can employ the card sorting technique reported by Nielsen and Sano (1994). Topics and tasks are written, each on a separate card. Then a sample of users is asked to group the cards according to their relatedness or semantic closeness. The result of this process is a collection of information chunks that designers can use to organize the site. Depending on the size of the site, each topic will have its own page in a task-logical order, or for large sites, its own subsite....

At this stage, designers begin the task of structuring the information and the tasks into a web site. They use the resulting chunks of information to organize the site into coherent pages, subsites, and related sites. Subsites organize a body of information that can be used in performing tasks without having to visit other subsites. The subsites of a given web site are related by a common user interface and a consistent look and feel.

For example, the CNNfn subsite....allows the visitor to get all financial news of the day without ever visiting the CNN news homepage. But because people who are interested in news are often interested in more than one type of news, the overall structure of a site should be such that a visitor can navigate to the homepage of any of the subsites from any site page by clicking on the subsites menu....

Once the structure of a site or subsites is established, then the designer should focus on identifying and creating types of pages within a site such as home pages, a log-in page, transaction pages, and feedback pages. Chapter 8, The Web Page, gives a more complete treatment of page selection and design.