I read just today at Mozilla's Blog that they received a Guinness Book of World Records certificate. This certificate is issued to Mozilla awarding the excellent services of the previously activist renowned team of having the largest number of software downloads in 24 hours.
This is how it reads with respect to the time period covered regarding the reward by Guinness at the official Mozilla blog -- "From 18:16 UTC on June 17, 2008 to 18:16 UTC on June 18, 2008, 8,002,530 people downloaded Firefox 3."
You can read the full story of the official announcement hereand you can follow the tweets of the declaration and the awarding picture here.CONGRATULATIONS!!!