From the homepage:
The Web Gallery of Art is a virtual museum and searchable database of European fine arts from 11th to 19th centuries. It was started in 1996 as a topical site of the Renaissance art, originated in the Italian city-states of the 14th century and spread to other countries in the 15th and 16th centuries. Intending to present Renaissance art as comprehensively as possible, the scope of the collection was later extended to show its Medieval roots as well as its evolution to Baroque and Rococo via Mannerism. Encouraged by the feedback from the visitors, recently 19th-century art was also included. However, we do not intend to present 20th-century and contemporary art.
The collection has some of the characteristics of a virtual museum. The experience of the visitors is enhanced by guided tours helping to understand the artistic and historical relationship between different works and artists, by period music of choice in the background and a free postcard service. At the same time the collection serves the visitors’ need for a site where various information on art, artists and history can be found together with corresponding pictorial illustrations. Although not a conventional one, the collection is a searchable database supplemented by a glossary containing articles on art terms, relevant historical events, personages, cities, museums and churches.

The Web Gallery of Art is intended to be a free resource of art history primarily for students and teachers. It is a private initiative not related to any museums or art institutions, and not supported financially by any state or corporate sponsors. However, we do our utmost, using authentic literature and advice from professionals, to ensure the quality and authenticity of the content.We are convinced that such a collection of digital reproductions, containing a balanced mixture of interlinked visual and textual information, can serve multiple purposes. On one hand it can simply be a source of artistic enjoyment; a convenient alternative to visiting a distant museum, or an incentive to do just that. On the other hand, it can serve as a tool for public education both in schools and at home.
The Gallery doesn’t own the works in question and so resolves the copyright issue thus:
The Web Gallery of Art is copyrighted as a database. Images and documents downloaded from this database can only be used for educational and personal purposes. Distribution of the images in any form is prohibited without the authorization of their legal owner.
The Gallery suggests contacting the Scala Group (or Art Resource, Scala’s U.S. representative) if you need rights beyond educational and personal purposes.
To see how images are presented, view 10 random images from the database. (Warning: The 10 random images link will work only once. If you try it again, images briefly display and then an invalid CGI environment message pops up. Suspect if you clear the browser cache it should work a second time.)
BTW, you can listen to classical music in the background while you browse/search. That is a very nice touch.
The site offers other features and options so take time to explore.
Having seen some of Michelangelo‘s works in person, I can attest no computer screen can duplicate that experience. However, if given the choice between viewing a pale imitation on a computer screen and not seeing his work at all, the computer version is a no brainer.