If you are expecting some downtime on your website - perhaps you might be moving web servers or need to perform some server maintenance? If this is going to happen, and you know about it in advance, then there are some steps that you can take to prevent your site being re-indexed by the Search Engines at just the wrong time and protect all those SEO results you have been working to maintain and improve by getting the website to report a 503 header status.

First off, I’ll give a bit more info about why we want to do this. A “normal” web page returns what’s called a 200 header status. This tells search engines and browsers that this page is a normal webpage and is “ok”.

A web page that has been permanently removed reports a header status of 404. This is why it’s important to have a functioning error 404 page, because when it is done badly, an error page can return a 200 status and tell search engines that an error page is actually ok, when in fact it isn’t.

However, if possible, we don’t want your site when it’s down to return a 404 status, because if a search engine crawls the website at this time, it may think its permanently removed.

Other status codes that you may well have heard about refer to redirects. There are 2 common header status’s for redirects – 301 and 302. A 301 redirect tells search engines that a page has PERMANENTLY moved, and a 302 redirect tells a search engine that a page has TEMPORARILY moved.

Another status code that many web searchers occasionally come across is a 500 code. This is a server error, when the website is unavailable at the time of visiting.

Without taking any action to put this in place, its normal that by default the status code returned during the site downtime will either be 404 or 500. These are common error messages when this occurs, but there is potential, if the search engines crawl the site at this time, that they may well think the site has gone, which could potentially have a devastating effect on your search engine rankings.

If it's possible to do so, the best method to prevent any problems is to get the site to return a 503 status – this tells them that the site is temporarily unavailable – and lets Googlebot know to check back later. This guidance comes from the Google Webmaster Blog from a couple of years ago, but is still relevant now. Its also possible to tell the search engines when to expect content back on the site using a “retry-after” command.