________________
Simply put, by hosting content from another page, you may be breaking Copyright / Intellectual Property permissions.
Be sure you have permission to place the content of the guest page on your host website!
________________
Especially for alternative-access methods such as those used by people with disabilities.
By placing content in an iFrame, for some users it acts like requiring the user to go to a different page.
This may be exactly what you want, but often it is the opposite:
For a typical user, the content is all organized visually in the same space; but for some users that visual organization does not exist!
To them, one part appears on one page, and the other part on a whole different page.
In the case of media, such as playing music or video files, that works very nicely, which is why iFrames currently exist.
You need to be sure that the guest content, while for many, is related to the host content, it still makes sense when viewed as Stand-Alone content - as if it is on a whole different page.... which it is.
________________
- This code can work from two locations, but it does not work the same for both!
Case-1: both use https://www.mydomain.org (assuming default of web port)
Case-2: If any part differs, say http vs https, or www.adiffertndomain.org, or music.mydomain.org or www.mydomain.org:8888