What do HTTP status codes mean for search engine optimization?
Many HTTP status codes are of great importance when it comes to search engine optimization (SEO). The 404 code does not just mean that the requested site cannot be found, but also that search engines can’t crawl the content. Just like with human visitors, search engine bots are also forwarded to different content. For SEO reasons the 301 code is displayed since link strength maintenance is of great importance. If the search engine crawler finds a 301 status code during a web address request, the invalid address will be deleted from the search index and a redirect then takes place.
The link strength of old pages doesn’t get lost in the process but is transferred to the 301 forwarding destination. This is especially useful if the old page had been the destination of incoming links and you want the acquired authority and strength to be transferred to the redirection destination. The 302 status code behaves differently since it only displays a temporary redirect so the old address stays in the index. The link power of existing backlinks isn’t transferred to the redirection destination in this case.