We investigated the task processes which hinder people with intellectual disabilities (ID) when using the human-computer interface. This involved testing performance on specific computer tasks and conducting detailed analyses of the task demands imposed on the participants. The interface used by Internet Explorer (IE) was standardized into 16 tasks (161 subtasks). A total of 57 people with ID completed all the tasks. The task demands of each subtask were analyzed and rated by an expert panel review. Results indicated that the 16 identified tasks to have varied levels of difficulty. Participants' performances were differentiated by two tasks: general motor functions and use customized bookmark. The majority of the tasks required visual acuity, vigilance, orientation, and basic sensori-motor abilities. The more difficult tasks were associated with higher levels of working memory and recognition of Chinese words. The model of identification, response, and execution was useful for analyzing the IE tasks. Successful IE performances appeared to be determined by the match between the participants' abilities and the task demands. The findings shed light on the use of task-specific screening tests and on the design of ability-specific training programs that enhance the computer competency of people with ID. (Contains 1 figure and 8 tables.)