There are four types of art instruction sites on the web:

1. Offshoots of the major accredited art academies and universities who have created a separate department to offer online art courses. These courses tend to be very expensive. Individual units are in the hundreds of dollar range, with complete programs up in the ten to twenty thousand dollar range. Their programs are comprehensive, giving you up to three years of training. Usually though they offer a combination of self-study and instructor feedback. The quality of the knowledge is relatively good.
2. Personal sites of professional artists. Most of these sites only have a few videos for sale, and maybe a few general purpose books. The instruction is usually in the form of a demonstration, in which a lot of principles are covered, but not in any depth. The videos tend to be long and can take several hours at a time to watch. This makes them very difficult to use as quick reference material. The quality of the information ranges from excellent to mediocre, depending on the expertise of the artist. The knowledge from the best of these surpasses that of the accredited art academies and universities because they are produced by highly trained professional artists, rather than academics who may or may not have the practical experience to backup their theoretical knowledge. The only way to judge the quality of these materials is to do a lot of research on the artist. If the artist has exhibited in several museum shows, this is a reasonable indicator of quality. If the artist is represented by one or more major galleries, this is another good indicator, although it is best to check out the quality of the gallery as well. Be aware that not all great artists make great teachers and vice versa.
3. Sites created by amateur artists whose main goal is to entertain, rather than to teach. There are many of these on the internet. While fun to watch, you will pay a lot of money for these courses, but learn very little that you cannot get from picking up a few art books at your local library.
4. Sites created by internet entrepreneurs, which appear to be created by a professional artist. Often if you do a search for the name of the artist, you will find several warning postings on art forums. You will also not find any independent reference to these artists when you do a search for their name. Neither will you find any independent references to major galleries or museum shows. These sites often can be recognized by a hard sell type of prose and should be avoided.

Compare to the top academic institutions, the instructional design of the Virtual Art Academy® course materials is at the same level of quality as the best programs delivered by an accredited art academy or university, since the instructional methods used in the course materials are derived from the methods used in universities. However, the quality of the content of the Virtual Art Academy® course materials is at a higher and more in-depth professional level. This is because the Virtual Art Academy® are all prepared by a full-time professional artist, and not by an academic.

Compared with individual workshops given by professional painters, you will find that the breadth of the Virtual Art Academy® materials is much wider than you will find on workshops given by individual professional painters. That is not to say that there is no value in taking workshops with professional artists. On the contrary, provided you select the right artist, there is great value in the one-on-one teaching approach you get in a workshop with a professional artist. The main difference is that to get the same breadth as the Virtual Art Academy® materials, you would have to take about fifty workshops, and even then you would have to organize your notes from those workshops into at least five hundred pages of typewritten notes and drawings. It would take you from five to ten years to do that based on my experience.