At mozillaquest.com: The Mozilla Organization has added an additional Milestone release to its Mozilla Development Roadmap and release schedule. Milestone 0.8.1 was added in between the recent 0.8 release and the upcoming 0.9 Milestone. It replaces and pushes-back the Mozilla 0.9 release date in the Roadmap schedule. That in turn pushes back the Mozilla 1.0 release date.
This new Roadmap schedule sets Milestone 0.8.1 release for 19 March 2001 and Mozilla 0.9 release for 23 April 2001. Please see Table 1.
Milestone 0.8.1 was added to the Roadmap schedule in order to allow the Mozilla developers time to fix more bugs prior to the Mozilla Milestone 0.9 release. In part this additional bug-busting round is because Mozilla 0.9, in addition to being a development Milestone release, also serves more or less as a beta branch-point for those people developing embedded Mozilla-based products that want to have a beta of their products