A solution I have found that works well uses the Sling 404 handler to fake PIE.htc. First, follow these instructions to set up PIE.htc in CQ: https://gist.github.com/msulliva/5971565. Second, create a Sling 404 handler, using instructions found here: http://dev.day.com/docs/en/cq/current/developing/customizing_error_handler_pages.html. Third, ensure your css behavior() points to just "PIE.htc" (not required, just recommended). Finally, at the top of the 404 handler put: if (request.getRequestURI...