Assessing Web site usability can be complex, because the medium can be both a document and a 'software product.' Documentation usability testing asks how headings, page elements, and index entries help users find the content they need, and whether that content is useful. Software usability testing asks how well the user inteface supports users’ job-task activity, indicates functionality, provides navigation signposts and program status, and prevents errors. A Web site must meet a combination of these goals—links should lead to the content that users seek, through pathways that users can easily follow without reaching a dead-end or getting lost.
Hinderer, Deborah and Laurie Kantner. STC Proceedings (1998). Presentations>Usability>Web Design