New Site Design - SEO Perspective

A new site design often means new content, either added to pre-existing pages or implemented on entirely new ones. This content needs to be properly optimized for the search engines. Pre-existing pages that were formerly optimized are now out of whack because you have added in new material that affects the density levels of those pages. These have to be properly analyzed and adjusted for your relevant key messages. New pages need to be optimized in sync with the rest of the site.
In most cases with a site redesign, the URL and directory structure changes completely. This means your pages in Google's index will no longer exist. Any positive traffic flowing to these pages will stop dead in its tracks. Place 301 redirects on the heavy hitter pages to salvage the search traffic currently associated with these pages. This will literally tell the spiders "sorry, this page has moved permanently. Please forward all traffic (and hopefully PR) to the redirect target and mark 'this one' for removal." Relying on your pages to naturally 'fall' out of the index will cost you dearly in lost traffic, and this is avoidable.

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