When creating websites and other interactive projects you first need to understand the intended user. Normally you are targeting a group of users that include individuals with similarities but varying demographics. You will probably have a primary and secondary group. In order to better understand your user you create personas. However there are commonalities in how individuals learn and perceive, these commonalities provide a useful set of considerations for web design.
The most important aspect is for your site to be user friendly and that the visitor be able to interact with your site effortlessly. Understanding how individuals perceive their world will help you create more effective designs.