Hi,

One way is to block access to duplicate content through robots.txt, i.e. if your category content is the same as your sub category pages, you may want to consider blocking the subcat pages from being indexed. Also, you may want to consider adding rel="nofollow" to sub category links.

Of course, the other point of view is that the duplicate content won't have a negative effect as such, the duplicate pages will just be filtered out, or google will choose the more "relevant" page.

__________________
Girlz Night - professional hair and beauty products
Web design glasgow - from Thin Denim