I want to change some of my posts from one catagory to another but they are all alrdy sitemaped, i was wondering how this will affect my site. will those posts still come up when searched or will url not be found... im a newb so plz help me understand how this will affect my site thanks
If your internal pages aren't getting rankings it shouldn't effect your search engine traffic too much. If you were to use just the postname for the page filename, changing the category wouldn't effect the url structure.
It depends on the structure of the URL. If the URL includes the category name, then the old URL will remain indexed until the search engines index the new pages. You could redirect the old pages to the new pages if there getting good rankings.
my url does include catagory name... but one thing i was worrying about was "duplicate content" if my post is alrdy indexed then gets indexed again will that be repeat or will the engine automatically delete the previous post from its index ow ya.... if i place a post in more than 1 catagory would that be duplicate content?
Only using a single category is best practice to avoid the duplication issue. I'd also remove the date field from the permalink and then use the robots.txt file to exclude Google from spidering the date based archives. A sweeping change, and one I've just made and am starting to see results, is to completely change the permalink structure and then 301 the old URLs to the new structure. I covered it recently in this post. It's only been a week but already my supplementals have dropped by around 15%.