Not as dramatic as Wikipedia (as in stop offering Firefox all together), Mozilla changed its usual white background default page (search page) to a blacked-out version displaying a modified graphic.
UserAgent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.7; en-US; rv:1.9.2.25) Gecko/20111212 AlexaToolbar/alxf-2.14 Firefox/3.6.25
