We all have to deal with 404 errors. Matt covers 404 and 410 errors and how to use them.

Google’s head of search spam, Matt Cutts, posted a video today explaining the difference in how Google handles 404 and 410 error status codes.
Both 404 and 410s are errors for a web page or document not being available, however a 410 is defined as “gone” forever. So 410s are more of an explicit response from the server telling you a page is really gone.
Google handles them slightly differently. With a 404, and some of the other 4xx status codes, Google will “protect” the page and not mark it as removed for about 24 hours. With a 410 status code, Google will mark the page as gone as soon as the error is noticed by GoogleBot.

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