Retaining ranking while changing extensions

[haggul]

I have a site which is currently all PHP and am looking to convert it to ASP.Net - it's got some good Google rankings as it's a niche kind of site and so want to protect that in the move.

I was thinking of tweaking IIS settings to process the .php pages through the .aspx engine, but then Visual Studio is a pain with extensions that are not what it's expceting for the coding model.

If I bite the bullet and change the page extensions what is the best way to migrate and retain the Google goodwill that exists? I am guessing some sort of redirects but I've never really had to get involved in that kind of thing.

Essentially the current product pages for example are simply product.php?PID=1234 and the new page would be Product.aspx?PID=1234 so can I do redirects in script based on dynamic URLs?

Many Thanks.

[tedster]

If all you are doing is changing the extension, and the rest of the filepath remains exactly the same characters, then it should be easy to write a script that 301 redirects from the old url to the new - and thats the essence of what you want to achieve, the 301 redirect. Just that much should keep the dip in traffic under control.

Some comments:
1. Consider how you might rewrite the urls so that they are now "extensionless" - this will futureproof your urls from any need for more rewriting in future years.

2. I've found it wise, especially on larger sites, NOT to redirect every URL. Rather, I do a study of what the key urls are (good entry traffic or strong backlinks) and only redirect those. The rest can go 404 and Google will quickly spider and find the new urls. With this approach, you avoid some of the issuse that we are discussing in this thread about 301 redirects [webmasterworld.com].

3. Have a test area where you can verify the new version of the website before you release it to the search engines. I've never seen an error free revision on the first try, and trying to fix problems AFTER they show up on Google is a recipe for extended ranking problems.