To avoid poor rankings in search engines, it is important to identify and remove dead links from your web pages. By promptly killing those dead links, you will also please your visitors!
Many web development software packages including Expression Web (from Microsoft), includes functionality to identify dead links. A number of free link checkers are also available on the Internet.
This link checker is W3C's easy-to-use HTML validation service, based on an SGML parser.
Submit Express offers a dead link checker and number of other tools for the webmaster.