Digital or electronic content, such as e-books, online documents, photographs on Web sites and electronic databases are subject to the same copyright protections under the Copyright Act as non-digital, traditional or analog works. Many people assume that online content found on web sites is not subject to copyright law and may be freely used and modified without permission or think that online content is not protected unless it carries a copyright notice. This is not true.
Before using content from a web site, you should determine the copyright status of the web content and, if necessary, obtain permission from the copyright holder. If you intend to post copyright-protected content on a web site, you are required to get permission from the copyright holder.
In addition, some think that you donít need permission to link another web site to your site. A link from your site to another web site, especially to a page other than the homepage, may need the consent of that web site's owner. U.S. law is not clear on this issue. In an effort to be safe, many organizations only link their own sites to the public home pages, rather than the internal pages of other web sites. To ensure compliance, obtain permission even to link to another web site's home page.
The Copyright & Fair Use at Stanford has an excellent resource on using web sites content and how to obtain permission.