Source code for all Mozilla products can be searched and viewed online with the lxr search engine.
Firefox Source Code
- Firefox 1.0.* is in the Aviary 1.0.1 lxr branch
- Firefox 1.5.* is in the Mozilla 1.8.0 lxr branch
- Firefox 2.0.* is in the Mozilla 1.8 lxr branch
See also Firefox Branching Plan.