This response code is used to indicate that the server cannot find anything at the requested path.

404 simply indicates that nothing was found, and is often used to display a user facing page informing the visitor that nothing could be found.

Custom error pages are great tools to help capture otherwise potentially lost visitors.

For an example of a custom error page, see Northrook.com's error page.

This response code is used to indicate that a response was successful. It is cacheable by default.

200 OK is used as a response code for several request methods, including: GET, HEAD, POST, and TRACE.

This status code is used to inform the visitor (both humans and bots), that the page in question is temporarily located elsewhere. This forwards everything to the address provided along with the status code.

Most relevant in relation to Search Engine bots, as they will be instructed not to update the address found on search results.

This status code is used to inform the visitor (both humans and bots), that the page in question has been moved permanently. This forwards everything to the address provided along with the status code.