This attribute instructs browsers to treat the iFrame's content more like inline markup than it would otherwise. Specifically, this means:
- Hyperlinks navigate the parent context
- The parent's stylesheets cascade in (importantly, the inverse is not true)
- More "neutral" rendering, roughly equivalent to declaring:
scrolling="no" marginwidth="0" marginheight="0" frameborder="0" vspace="0" hspace="0"
The user experience of following hyperlinks is drastically altered in supporting browsers.
Should be avoided because of the lack of browser support (Chrome 20-26 had partial support behind a flag, though this was later removed).