I have contributed to Firefox and Servo and found both communities to be incredibly patient, tolerant and friendly.
You can find bugs in bugzilla (firefox) or github (servo) that are labelled as suitable for newbies, my advice is to try and build it first then pick one up and go for it!
You can find bugs in bugzilla (firefox) or github (servo) that are labelled as suitable for newbies, my advice is to try and build it first then pick one up and go for it!