The referrer feature is based on events but applied
to classic navigation. When the user leaves an ItsNat page
(using events and referrer enabled, see
ItsNatDocumentTemplate.setReferrerEnabled) by clicking a "normal" link or
submitting a "normal" form navigating to other ItsNat page, in load time
ItsNatDocument of the previous page.
This document may be used to import DOM code or to copy user data
to build the new page (almost any ItsNat object implements
designed to contain user data alongside ItsNat objects) before the
previous page is destroyed (replaced with the new page in the browser).
The referrer object is very useful to detect the back and forward buttons, the "self target"
(a link or form targeting to the same page) or the reload button.