The HTTP Referer header is a header that is transmitted with the HTTP request when a link is clicked on one page and a new page is requested through HTTP.
This allows Analytics to track where a user is coming from or what path a user is following on the site.
HTTP Referer headers are not transmitted when following a link from an https: page to an http: page.
Since sites like google.com are running on https: , it is sometimes impossible to see search referals coming from them.
Created by • Last edit by on Jan 08, 2015