We successfully contested a street sweeping ticket because the sign we were parked under said street sweeping ran through 11/30, not 12/31. We took a photo and the city said 'Well. You were wrong, but we'll let it go this time.'

Not our fault they missed a sign (we had just moved, and never parked under the other signs, so had no idea they were different), and they were really bitchy about it, but we got it dropped.