Embed Iframe is a Wordpress plugin that will let you embed
iframe – an HTML tag that allows a webpage to be displayed inline with the current page, in a Wordpress post. Although an
iframe can lead to a complicated website, it can be very effective when used appropriately.
You can find full details of installing a plugin on the plugin installation page.
[iframe url width height]
You cannot embed a URL which carries X-Frame-Options header with the value DENY.