A web user is looking at page A. He clicks on a link for page B. That page has a META Refresh to page C. What is the value of HTTP_REFERER for that last request? What if the redirect was a Status 307? Or a location.replace() JavaScript call? What if he’s using Opera? I’ve been doing some redirect referer tests this week and I have results for some the most common browser/OS combinations. I hope to expand them further.