Best error message EVER

Disable your sarcasm detectors; none follows.

mymsi.wxs(16) : error CNDL0014 : The File/@Id attribute's value, 'foo-bar', is not a legal identifier. Identifier's may contain ASCII characters A-Z, a-z, digits, underscores (_), or periods (.). Every identifier must begin with either a letter or an underscore.

I don't know whether this is the Microsoft MSI XML compiler or the open-source tool Wix. But whoever is responsible for it, you get the Best Error Message of 2006 Award. This message is perfect: it tells you exactly which part of the file was wrong, and the rule you need to follow to fix it. If every error message were this informative, we wouldn't need documentation.