In this tutorial we are going to demonstrate a way to use multiple separators within the_category tag's $separator string, specifically focusing on a separator and a leading prefix for the following category. In order to list the post category ( or categories as the case may be ) all that is needed is to include the the_category tag: http://codex.wordpress.org/Template_Tags/the_category

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WordPress: the_category Using Multiple Separators Between Categories …