This document discusses how to preserve a website's search engine rankings when moving to a new site design or platform. It recommends (1) crawling your current site to audit pages, (2) evaluating your site's technology, (3) tracking changes between the old and new sites, (4) checking internal and external links, and (5) using 301 redirects to direct traffic to updated pages on the new site. Following these steps can help Google recrawl and index the new site, maintaining traffic from search engines.