The code for all projects in the Mozilla family (such as Firefox, Thunderbird) is combined into a single source tree. The tree contains the source code as well as the code required to build each project on supported platforms (Linux, Windows, Mac OS, etc).
Getting the Source Code
You can download a a snapshot of the sources or you can check out the current sources from CVS.
The Source Code Directory Structure
There used to be content here, but it was mostly wrong, although some of the last edits had some useful material. It should be replaced by content from and/or .
Also, it should be clear what the scope of the list is -- things that are pulled by client.mk, or everything in the Mozilla CVS repository?