What does HeaderControlRevived do? It provides control over HTTP headers (User-Agent, Referer and Accept-Language) on a per-site basis.
The purpose of this add-on is to rewrite values of HTTP headers that Mozilla Firefox sends to websites during its daily usage. It also allows users to have unique per-site preferences. Currently the following can be modified:
Want to learn more about this add-on for Firefox? Check it out on the Firefox Add-ons website.