HTTP_REFERER can't be obtained

I run request.env in view and no HTTP_REFERER there. How i can get
HTTP_REFERER ? I trace using "Live HTTP Header" in Firefox, the referer
is obtained. I tested to IE, Mozzila, Opera, Gecko & Firefox, the
result is the same. Referer is traced but http_referer in rails still
can't be obtained.

I am using rails 2.0.2 & ruby 1.8.5, here the list of @request.env in my
view :