During the last several years, the internet-based educational materials – although with contradictions and temporary letdowns – have spread significantly. The educational websites, frequently enough, only mediate the access to and download of essentially static educational materials of different formats (doc, ppt, pdf, etc.). Recently, however, the number of those educational websites is definitely growing that provide real interaction (interactive learning, problem-solving, curriculum-tests, etc.). A frequent negative experience is that simultaneously with this marked quantitative increase the (professional, didactic, usability, ergonomic, etc.) quality cannot keep pace. From this it follows that there is a growing need for methods capable of assessing the quality of these electronic materials and services in both theoretically and practically well-established ways. We are witnessing therefore numerous attempts to measure quality - as objectively as possible – based on mainly questionnaires, scales, interviews or structured observations. After all, it can be stated, that this problem is far from being solved.

This very paper – together with the two other related empirical studies published simultaneously with which this paper compose a thematic unit – is to provide an introduction into the problems of applying web-mining methods in education.