It is not necessary that the notes contain all the details on a subject, they can be supplemented and updated during the lecture.
Professor's notes are authorized educational materials, signed by the author/professor. They do not, however, have the gravity of an officially proscribed material, since they did not pass the review procedure necessary for approval of an educational material.
They can be found on the web most often as a PowerPoint presentation, although they also appear in other formats such as PDF, scanned transparencies etc. These notes are, of course, a valuable source for the students through which they get a glimpse at the teacher's view on the subject.
This is by far the easiest way for the professor to disseminate educational materials to his/her students. Notes are a part of every professor's preparation, they are flexible materials which can be easily supplemented from one academic year to the next, and if author decides so, its use can be regulated through login/password administration.
We recommend the professors to remove the last year's version from the web before the new lecture cycle. That enables them to freely supplement the materials used during previous academic years. Experience has shown that class attendance is better if materials cannot be found on the web before the classes. For that reason it is recommended that the professor's notes be supplemented after each lecture. After the lecture cycle finishes, a collection of professor's notes is left on the web, so that students can have access to it during preparations for exams.