You are problably here because you clicked on a link about embedded document problems.  Some browsers are capable of the more sophisticated operations, and some are not.  Some cannot see the document at all.  At the time this page was written, these are our findings for browsers freshly installed with no extras or plugins:

BrowserDocument visibleDocument options
Firefox Yes Yes
Seamonkey Yes Yes
Safari Yes Yes
UC Browser Yes Yes
IE & Edge
Yes No
Opera Yes No