HTTP referer
In the most common situation, this means that when a user clicks a hyperlink in a web browser, causing the browser to send a request to the server holding the destination web page, the request may include the Referer field, which indicates the last page the user was on (the one where they clicked the link).The misspelling of referrer was introduced in the original proposal by computer scientist Phillip Hallam-Baker to incorporate the "Referer" header field into the HTTP specification.[6][7] The misspelling was set in stone by the time (May 1996) of its incorporation into the Request for Comments standards document RFC 1945[8] (which 'reflects common usage of the protocol referred to as "HTTP/1.0"' at that time); document co-author Roy Fielding remarked in March 1995 that "neither one (referer or referrer) is understood by" the standard Unix spell checker of the period.[11] Some proxy and firewall software will also filter out referrer information, to avoid leaking the location of non-public websites.Some proxy software has the ability to give the top-level address of the target website as the referrer, which reduces these problems but can still in some cases divulge the user's last-visited web page.Generally, Internet-security suites blank the referrer data, while web-based servers replace it with a false URL, usually their own.