What is 404 versus a 410 ? Matt cutts, Does Google do anything different when encountering a 404 versus a 410

First of all, Matt explains what a 404 and a 410 is. These refer to HTTP status codes; whenever a browser or Googlebot asks for a page, the website sends back a status code. For example, a status code of 200 means everything is fine, whereas a status code of 404 means the page was not found. And then there’s a 410, which means the page is permanently gone. Matt says Google does treat 404′s and 410′s a little differently, but for the most part you shouldn’t worry about it.
Matt goes on to explain how these types of status codes are treated when crawled by Googlebot. If Google crawls a page and sees a 404, they protect the page for 24 hours in the crawling system in case the 404 was unintentional. If Google crawls a page and sees a 410, it’s assumed that status code is intentional because a webmaster would have had to manually go in and input the 410 code to indicate the page is gone. Rather than protecting a page with a 410, it’s treated as an error. Matt says Google still may go back the page is truly gone, but for the most part if you know the page is gone and not coming back it’s ok to serve a 410. If a page is gone, but may be coming back, it’s ok to serve a 404.
Those are the basic differences, and Matt emphasizes a second time not to worry about them too much. Source from : http://www.searchenginejournal.com/matt-cutts-explains-google-treats-404-410-status-codes/101255