More than 8m people downloaded Firefox 3 in the first 24 hours of release

"Thanks to the support of the always amazing Mozilla community, we now hold a Guinness World Record for the most software downloaded in 24 hours. From 18:16 UTC on June 17, 2008 to 18:16 UTC on June 18, 2008, 8,002,530 people downloaded Firefox 3 and are now enjoying a safer, smarter and better Web.
Ever since Firefox was launched in 2004 we've relied on our community to help us spread the word, and thanks to projects including crop circles, newspaper ads, giant stickers, videos, blogs and more we now have over 180 million users in more than 230 countries.
Source: Firefox statement, June 2008