When a Web site visitor requests a nonexistent URL from a Web server, the server sends the visitor an error page. This event is recorded as a 404 Not Found error in the Web server log. Encountering an error page is a frustrating experience for a Web site visitor, and studies have indicated this is a leading reason why people leave Web sites. In addition to reviewing 404 error reports for your site, you can identify broken links using a link checker or validator. Many tools are available for checking Web links.
Products range from commercial software to freeware.
Some products can be installed on your own computer system so that you can check links before you put a page on the Web. Others operate as online services and can only check links on pages that are accessible from the Internet. Results are available interactively or by e-mail. Monitor the results interactively or review them after you receive e-mail notification that the analysis is complete. Results are returned by e-mail in a zip file.