Hi all fellow HNers,<p>What is the best way to keep a website's search engine ranking while rebuilding it with a better url structure?<p>The case in point is a potential customer that has a very messy and broken website running on PHP. It fails on many levels including not using descriptive urls (e.g. /Product.php?10) and very bad table based markup.<p>I wanted to develop a online shop on Ruby with better urls and better on page SEO but that would break the current url structure.<p>Will doing 301 redirects from every old page to the its new sibling harm in terms of search engine ranking?<p>Thanks<p>Filipe Moreira