Sometimes when you do a site redesign or a company rebranding, you also change your domain name. But sometimes publishers are simply changing the domain name, and everything else (except for perhaps branding changes) stays the same.
One of the more challenging aspects of a domain name switchover is the potential loss of trust the search engines attached to the old domain. When you make a move, trust does not always shift that easily to the new domain. Another issue is that if there were any keywords present in the old domain name that are not in the new domain name, you may see a negative impact for search terms that include those keywords. For example, when Matt Mullenweg, founder of WordPress, switched the domain of his personal site from http://photomatt.net to http://ma.tt, he lost his #1 ranking in Google for Matt.
Due to a lack of aging, the new domain may be slow to rank. Although the site’s relevance and inbound link profile (including the links 301-redirected from the old domain) may suggest a high ranking for some search queries, because the new domain is not trusted yet the rankings are suppressed, and traffic is much lower than it would otherwise be.
This is one reason for the recommendation we will make in the upcoming best practices list to get the most important links to your old domain switched over to your new domain. One other tactic you can try is to ...