Stephan Downes talks about what he considers the three most important principles for effective e-learning :

No doubt there are other aspects of effective e-learning. Pedagogical theorists will talk about scaffolding, talk about learning objectives and outcomes, talk about practice and examination, and more. In various contexts these are all important and will play a significant role in determining the success of failure of a given learning enterprise.

None of these, though, are as central to the design of effective learning as the three criteria listed above. By ensuring that e-learning content is interactive, usable and relevant a designer can be virtually sure that the e-learning outcome will be a success. or at the very least, appreciated by the learners. Who are, after all, the final judge.

...via elearningpost