Headings or other essential information should be repeated on each page rather than assuming that users have already come across the information at a higher level. The interface is the visual screen that the student sees and interacts with. The placement of graphics, the use of tables, frames or drop down lists, the choice of colours, the size and type of font face, should all be designed to facilitate the learning experience, not impede it. Consistency is one key to a good interface. It is confusing when an icon means different things or a navigation button changes position.
Clarity is another important consideration.
Interface and graphic elements should be easy to recognise and unambiguous. The dilemma is how much text to provide on one screen so that it avoids both problems. The solution is probably to provide text in sense bites' so that a page forms a natural unit, making it harder for the user to lose their place in the text, and making it less frustrating to wait for the next page to load. Larger documents can take advantage of hypertext, where the core of the paper is presented on the first page with links to definitions, references, expanded arguments, examples or differing points of view. In writing text for the web it is important to think in terms of networked layers of information, rather than a linear progression.