410 for WordPress is a plugin by solarissmoke that will issue a HTTP 410 response to requests for articles that no longer exist on your blog. When you delete a post or page, it records the URL for that page and issues a 410 response when that URL is requested. You can also manually manage the list of obsolete URLs.
The HTTP Specification defines the 410 response header for use when a resource has been permanently removed. It informs robots visiting your site that the requested content has gone, and that they should stop trying to access it.
Plugin FAQ: http://rayofsolaris.net/code/410-for-wordpress#faq
Download and info: http://wordpress.org/extend/plugins/wp-410/
