Retaining SE Rankings After Site Redesign

Am trying to keep SE Rankings after switching from ".html" to ".asp"

[topsider]

We have a website with excellent Search Engine rankings and we have just redesigned the site with all sorts of new functionality which is now utilizing ".asp" extension from the previous ".html" extension. Now I don't want to lose our position when uploading the new site to the server.

What do we need to do in order to retain this position? Are there any unforseen issues with this type of change on a website redesign?

Kind regards,
webmaster

[neuron]

there are lots of issues. rankings can be dramatically affected for sites that compete in a narrow range of keywords. you probably want to do permanent redirects from the old pages to the new pages, you want to update links from other sites to your new site.