Google’s head of search spam, Matt Cutts, posted a video explaining the consequences of a site going offline and how that can negatively impact that site’s ranking in the Google’s search results.
In short, a site that temporarily goes offline for a short period of time, such as less than 24 hours, should be fine. But a site that goes offline for an extended period of time, such as 48 hours or more, may see their site delisted from Google’s search results – at least temporarily.
The reason should be obvious to most of you. Why would Google want to send a searcher to a website that isn’t working? Google rather send the searcher to a site that might not be as relevant but at least a searcher can see and read.
Here is the video:
Matt also notes that when a site goes offline, Google will try to send those who are registered with Google Webmaster Tools a notification that there site is offline. These messages normally say something to the effect that GoogleBot is not able to access the site.
These notifications can help you ensure your site is up by informing the webmaster of any down time. Also, Pingdom offers a free website monitoring and alert system to notify you when your site is not accessible.
What about planned downtime for upgrades or site changes? We’ve covered that in our story on How To Blackout Your Site (For SOPA/PIPA) Without Hurting SEO.