Your mileage may vary

cav. [from the standard disclaimer attached to EPA mileage ratings by American car manufacturers] 1. A ritual warning often found in UNIX freeware distributions. Translates roughly as "Hey, I tried to write this portably, but who *knows* what'll happen on your system?" 2. A qualifier more generally attached to advice. "I find that sending flowers works well, but your mileage may vary."