WordPress is great at handling URLs and making them ‘pretty’ with custom permalinks. You can use almost any kind of URL structure for your website using the ‘Custom Permalinks’ tags. However, this fails in case you want to have permalinks that a plug-in should recognize and redirects you to the WordPress 404 page.
For example, if you have a page called calendar accessible via http://my-website.com/calendar which is essentially a page that is generated via a custom template or a shortcode, a URL like http://my-website.com/calendar/2010/march will lead to to a 404 page. The easiest solution to avoid this is to have a URL like http://my-website.com/calendar/?year=2010&month=march which given the rest of your website will look plain ugly.
We can however use the WP_Rewrite class and extend the set of rules that WordPress processes to ensure that our rule is processed like we want it.
We recently used this for one of our websites which you can view here Australian Shephard Dog Breed or Beagle Dog Breed
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