The 404 error, returned by a Web site, indicates that the page you requested was not found at the address indicated. This is a webmaster's nightmare, because it usually indicates a broken link (dead link), ie a link whose address has changed. Fortunately, there are tools to automatically verify the presence of broken links on a website.
W3C Link checker
The W3C provides a simple, online resource to find dead links on a page or a set of pages by following links recursively.
Convenient for rapid use (check the links on a single page), this tool quickly shows its limitations when analyzing all the links on a website.
Xenu's Link Sleuth
Xenu is a software which will help you to verify broken links of a website.
It displays the resulting list of URLs updated continuously, can be sorted by various criteria and can be a customized report!
Possibility to recheck the of broken links (in the case of temporary connection errors for example)
Reports in a single file or email
Support for secure sites with SSL ( "[https: / /]")