A Cre8asite Forums thread asks what are the search engine optimization implications of switching from ASP to PHP?
This is a fairly basic SEO question but it is a good one. This question applies to changing any URLs, not just from ASP to PHP. It is also from HTML to CFM or CFM to ASP and so on. It also includes changing a file name from abc.html to cba.html.
Search engines index pages. Pages are determined by their file name and extension and domain name. If you change any of them, it is considered a new page. So if you have a page at domain.com/filename.html and change it to domain.com/filename.php - it is a new page in the eyes of a search engine. If you have domain.com/filename.html and change it to domain.com/newfilename.html - it is a new page in the eyes of a search engine. If you have a page at domain.com/filename.html and you change it to domain.net/filename.html 0 it is a new page in the eyes of a search engine. By now, I assume you get my point.
What can you do? I would follow the same steps I laid out in Version 2: Relaunching a Site: SEO Considerations. You must set up 301 redirects from the old pages to the new pages, with dynamic sites, it may be easier, since there may be some database logic that you can set these 301 redirects up dynamically. You must set up custom 404 page not found error pages up for those pages you simply can't 301 or for the pages that you forget to 301.
Those are some of the basics when it comes to switching page extensions or pages in general.
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