Mozilla 1.0 was released on June 5, 2002, after more than four years of development as an open source project. This book was written so that all examples will work with this release and any 1.0.x maintenance release.
After the 1.0 release, two main development branches of Mozilla were created. The stable, long-lived 1.0 branch is dedicated to fixing bugs in the code of the 1.0 release. From this branch, periodic maintenance releases are labeled as Version 1.0.x. Every 1.0.x release is designed to be fully compatible with (though less buggy than) the original 1.0 release.
The other development branch is from the Mozilla CVS trunk. New releases from this development effort are labeled as 1.x and may include new features, changes to architecture, or other additions that help Mozilla evolve as a project.
These new 1.x releases may not be fully compatible with applications created to work with Mozilla 1.0 and the 1.0.x releases, but mozilla.org made a commitment to preserve frozen API compatibility (including XUL and XBL syntax) throughout the 1.x series until a future 2.0 release. See http://www.mozilla.org/roadmap/mozilla-1.0.html for details.
Because Mozilla itself is under active development, applications built on the framework may be affected when new versions of Mozilla are released. We recommend that you refer to mozilla.org's development road map for the latest information about the state of Mozilla; see http://www.mozilla.org/roadmap.html.
We also recommend that you use Mozilla 1.0.x versions when working with examples in this book. We encourage you to use the latest 1.x release as well so you can stay involved with the latest and greatest that Mozilla has to offer.