Your mileage may vary definition, from Internet Connection, Inc.

[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. More generally, a qualifier attached to advice. “I find that sending flowers works well, but your mileage may vary.”