When you think about SEO do you remember to think about how your website handles HTTP status codes? The odds are that you don’t. Your “page not found” probably returns a 404 (everyone knows about that one) but what about programmatic error pages or login pages? Search engines index pretty much anything that has a 200 status code. This means if you don’t pay attention you can end up with pages indexed & findable that shouldn’t be.
For example, if you are logged out, Washington Post’s newsletter page 302 redirects you to a login page that then serves a 200. This means a Google search for newsletters for washingtonpost.com gets indexed with the text from the login page. If they were to serve a 401 “Unauthorized” on the pages that require logins, these login pages would not be indexed. Use caution with that scenario though. It might be better to handle search engines differently than normal users so the content can be indexed.
This post was written by Michael Tougeron on June 11, 2009