Throughout the paper, the issues of individual differences in web-based learning, also known as online instruction, online training or distance education were examined and implications for designing distance education were discussed. Although the main purpose was to identify differences in learners' characteristics such as cognitive, affective, physiological and social factors that affect learning in a web-enhanced environment, the questions of how the web could be used to reinforce learning, what kinds of development ideas, theories and models are currently being used to design and deliver online instruction, and finally what evidence for the effectiveness of using World Wide Web (WWW) for learning and instruction has been reported, were also analyzed to extend theoretical and epistemogical understanding of web-based learning.