Source: http://www.searchenginejournal.com/5-common-seo-mistakes-may-making-redesign-website
A lot of businesses lose traffic after redesigning their website because of mistakes they make during the process. Here is a list of 5 common mistakes and how to avoid them.
Redesign your site the right way
1. Dev site is indexed, main site isn’t
Make sure that the content of your dev version site is explicitly blocked from appearing in Google’s index. However, make sure you don’t block the main version of your site.
2. Improper installation of analytics code
Be sure you install your analytics code properly as you redesign your site. Avoid creating a new profile and mishandling new subdomains; and check if the code gets carried over to the new site.
3. Recklessly changing your link structure and URLs
If you don’t absolutely need to change your URL structure leave it as is; be sure to implement permanent 301 redirects to appropriate pages, implement any content migration properly on subfolders, create a great 404 page with links to relevant information and follow SEO best practices on 404s and HTTP status codes.
4. Using new code and new features
Know about Google’s recommended implementation, alternatives for the same functionality, and the effect of different functionality on your search traffic.
5. Messaging is not aligned with your keyword strategy
Understand the impact of changing the title tags and on-page content to your website’s search traffic.