If a page on your site can be accessed with more than one URL (http://….), this can cause difficulties with the search engines, which might consider you’re repeating the same page over and over again, even though you’re not intending this to happen. The search engines may divide up the “strength” of the pages between the different versions they think they can see, and indeed, external links may be divided between the versions too.
But do you suffer from this problem? It’s hard to know. In Quickly Find Your Site Duplicate Content Issues on Daily SEO Tip there are a couple of ideas which might be worth investigating. I’d recommend following them up.
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