Can a rating go below 0?
I can't imagine it could even be zero, if I had to guess I would say 1 would be the lowest.
One of those limit as it approaches 0 deals.
What makes you ask this question?
Theroretically, it might. Practically, no. You would have to lose 99% of the time to somebody that loses 99% of the time the time against an average casual chess player in your family.
Can a rating go below 0?