Most websites do not allow their content to be loaded in IFRAMEs. The main reason is to prevent “web framing” in which a remote website frames another to get clicks. This is also applicable to SharePoint applications in which the frame options are set to allow SAMEORIGIN only which means that framing is only allowed to pages on the same domain.
In SharePoint, there is a way to enable your application to allow the pages to be rendered in an IFRAME. This can be done by adding the following Web part to the master or single page.
This webpart enables the SharePoint content to be rendered in an IFrame by websites hosted in other domains.
Also note that this meta-tag does not work on SharePoint 2013:
<meta name=”X-FRAME-OPTIONS” content=”ALLOW” />