The spirit of fair use is to promote education and research. Receiving a profit from the work is contrary to the spirit of the exemption. The criteria for applying the fair use exemption can be found in the section on fair use. As I understand it, an original work is automatically copyrighted once it is fixed in a tangible medium, i.e. published. By registering, the author is establishing the exact date that the work became copyrighted and to whom it was granted.
Registration affords the ability to collect monetary damages for infringements.
Without registration, a suit can only be used to prevent further infringement by the offender. All of the copyright concepts apply to electronic materials. In fact, publishers and authors are more concerned about web publishing because the audience is so vast and it is so easy to copy and distribute materials. You should remember that it is not necessary to post a copyright notice for the author to have these rights, even on the web. Yes, providing that it is a link and not done as framing.