Often companies ask us can changing web hosting to a new host damage their search engine optimisation. In the video below Matt Cutts of Google’s search engine team talks through the basics of what happens when you change web host.
If, in the process of moving web hosting, you also intend to migrate your site to a new content management system (for example you intend to migrate to WordPress which we do quite a lot for customers), then you must always make sure you do 301 redirects for the old site links. This tells the search engines where they need to find the pages on the new site and also lets them know that they should update their index with the new URLs.