Many Webmasters on several occasions try to move their website to a new domain. However, the prospect of a 404 error (File not found) negatively impacting their site rankings restrains most of the Webmasters to perform the transition. Yet again, Google to the rescue. Google has provided some tips on the Webmaster Central Blog for the site owners to follow while moving their website to a new domain.
A site owner should first test the move process by moving contents of one directory or subdomain. Then he should use a 301 redirect to permanently redirect those pages from his old site to his new site. This would notify the search engines, that the website has been permanently moved.
A Google search should be performed for the pages that have been added to the new site. If the SERPs show the moved pages, then it's safe to move the entire site.
In case the Webmaster is changing his domain due to site rebranding or redesigning, then the changing of the domain should be carried out in two phases. Firstly, the website should be moved and secondly, the site owner should launch his redesigning.
Both the external as well as internal links to the website should be checked. In case the original content included absolute links, then it would be wise to use a link checker to make sure that there are no broken legacy links on the site
To avoid confusion during and after the transition, it is always recommended that a Webmaster should retain control of his old domain for at least 180 days or for a minimum of 6 months.
The new website should be added to the Webmaster Tools Account and 'establish & verify' the ownership of the website. Next, a Sitemap should be created and submitted listing the URLs on the new website. This would enable the search engines to start crawling the new site.
The new as well as the old site should be verified in the Webmaster Tools and crawling errors should be monitored regularly. This will enable the Webmaster to keep a check as to whether the 301 messages from the old site are working properly or not. Also it will show whether the new site is giving any unwanted 404 errors.
Following these steps will aide in a smooth transition from one domain to another and also the ranking of the web site will be saved from being hit.