Firefox
Enable Firefox Debug Logging at Runtime
- Go to about:networking
- Click Start Logging
- Copy the file name where it says it is writing to
- Reproduce the problem
- Click Stop Logging
- Review the file mentioned above
Enable Firefox Debug Logging at Startup
- Open terminal
- Set environment variables:
- MOZ_LOG=timestamp,sync,rotate:200,nsHttp:5,cache2:5,nsSocketTransport:5,nsHostResolver:5,cookie:5
- MOZ_LOG_FILE=/tmp/log.txt
 
- Start Firefox
- Reproduce the problem
- Review the file mentioned above
Source
- Downloadable
source tarballs (under $RELEASE/source/)
- Online browsable sources