Every Web author, and even every Web user, should know the very basics of copyright. This document discusses them very briefly and gives links to more detailed resources.
Almost all countries have some copyright legislation. Although there is national variation, the basic principles are universal and based on international copyright treaties:
When using someone's work, either with his permission or on the basis of exceptions to copyright, you should normally mention the author and the source. The source can be specified using the title of a book (perhaps with more detailed bibliographic information such as an ISBN number), or a Web page address. For Usenet news articles, the name of the group, the author, and the date as given in the article are usually sufficient identification; but notice that it is possible, although a bit difficult, to refer uniquely to a news article on a Web page.
On Web pages, setting up a normal
usually needs no specific permission. It is comparable to
mentioning a book.
It simply refers to a page which is already on the Web.
(In special cases, especially on pages which use frames,
permission might be required.)
On the other hand, if you
embed something into your page
(such as an image using an
IMG element, or some music using
EMBED, or anything using
you need a permission from a copyright owner of the embedded
resource, as a rule.
The reason is that you are using a work in the context of
your own page; you are stepping into the area of
"communication to the public". More information:
When someone puts his work onto the Web, this act can be regarded as an "implied license" to access that work in manners which are normal Web usage, such as reading or viewing or listening to the work. Usually printing a page for personal use is acceptable, too. But the "implied license" does not extend to making several copies and distributing them, publishing the material in a book or copying it into your own Web page. For such acts, you need explicit permission from the author.
For more information about copyright in general and on the Web in particular, I especially recommend the following documents (of reasonable size):
The following list gives some other potentially useful links to further information about copyright in English. Please notice that some documents may describe national situation (e.g. in the United States) without making this clear.