"Every site owner and Webmaster has either contemplated or participated in a website redesign at some time in the history of their sites. Unfortunately the vast majority do not factor in the search engines and SEO when completing their website redesign. How many times have we seen people come to us after they have performed a site redesign only to see their search engine rankings tank?"
So true - and the #1 tip is don't redesign your site for the sake of redesigning it. Read more....