When we recently announced our intent to add a do not track header to Firefox, we focused on how it will probably be available in a future version -- Firefox 4.0. But what about people who would prefer to use previous versions of Firefox? How can you get the HTTP header into version 3.6, or even earlier versions?
Though we recommend using our latest and greatest product, there's an add-on you can install to add the "DNT: 1" header to older versions: Universal Behavioral Advertising Opt-Out (a.k.a. UBAO). The name is a mouthful, but its operation is simple: installing this add-on is like ticking the checkbox in new versions of Firefox to send a "DNT: 1" HTTP header with all requests your browser sends out.
There are other add-ons that send the header! AdBlock Plus and NoScript send the header too, but if you don't want the extra features that come along with those add-ons, UBAO is for you.