I'm using some url rewrite rules to get nicer .html urls with a part dedicated to the keywords for that page, but sometimes in the code I need to link to the same page the old-fashioned way, which is .php with parameters. My question is: does it count as duplicate content?
Yes, you can use mod_rewrite to eliminate the old dynamic php urls all together, however with a example of the site or some URLs that is as much as I can tell you.
Any time we use query strings (dynamic programming) to create a page, we use a "template". This template usually will contain a Header, LeftSidebar Navigation, Footer, etc. Then we add the "data" to the content section. It is very important that the total character count of the Header, Left Sidebar & Footer doesn't exceed ~50% or it will trigger a Dup penalty (Gray bar the page). What happens is that we us "common code" designs and that creates the Duplication. This happens in CMS systems, Shopping carts or most database driven Web applications. Hope this helps Also, the Mod Rewrite will not help or affect this problem. Consider using a Google XML Site map for query string submission. It will help.
You can block the old (dynamic) URLs in your robots.txt Google simply won't index URLs containing this or that dynamic part Here's how you can do it google.com/support/webmasters/bin/answer.py?answer=40367
Thanks, rocketfish, that's a solution I should definitively look into. I thought also about doing redirections in the .htaccess
All of you article writes, stop being shy and use 113Directory as depository for your articles as well.