Include It is a little old, consider to use Include Me instead: it has the same features but it uses the WordPress short code standards. You can read more on the Incude Me official page. Include It is a plugin that permits the inclusion, in a post or in a page, of any type of file (even a php script that will be executed). I use it to write some functionalities needed in some pages, without creating special template pages (that are theme dependant) and without using a “php code executor”. The inclusion can be forced to be within an IFRAME html tag. See the options page of the plugin for a deeper explanation and how to use it and the plugin official page.