I made the example in railscasts 117 #117 Semi-Static Pages - RailsCasts for clean urls and static pages and it worked fine.
After that I wanted to do a simple page cache with pages_cache and expire_page (as in railscasts 89 #89 Page Caching - RailsCasts). The page_cache works fine and it creates the pages in public folder, but the expire_page doesn't work for the permalink, it works for /:action/:id url, so I can't update the pages. I am thinking of doing it manually (delete the html file with plain ruby when a page is updated, instead of expire_page) or to make a button to enable/disable the cache... or is there a better way instead of this to make the expire_page work?