Users sometimes face a common and serious problem called disorientation, which is defined as the feeling of being lost in a web-based environment. It is important to determine the reasons for disorientation in order to make the students navigate more efficiently in these environments. The aim of this study is to investigate the relationship between navigation patterns, disorientation level and students' cognitive ability. For this purpose, an experimental research was designed and a 223-page Wiki environment was developed as a network structured hypertext environment. Sixty-nine university students' navigation processes including 6.880-row log data were recorded in order to measure their disorientation scores. We found that task complexity negatively affected disorientation scores. Disorientation scores decreased as the tasks became more difficult. Possible causes of the results are discussed.