If your new site has the same structure as the old - the same page and directory names for the same content - you can simply redirect the domain and all the URLs will be mapped to the new one. Otherwise you will have to create a separate redirect for each page, which will be a lot of work if the site is large.

Initially the new pages will probably not show any page rank at all in the Google toolbar, but your rankings in the search listings will be retained - which is what really matters. Your existing links will be credited to the new site.

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Bruce Townsend
Actinic ecommerce software, ecommerce website design