Make says "missing separator"

Q: When I invoke Make, it refuses to do anything and prints a cryptic message: "makefile:10: *** missing separator. Stop." Now what kind of excuse is that?

A: Unlike most other DOS Make programs which accept any whitespace character at the beginning of a command in a rule, GNU Make insists that every such line begins with a TAB. (Most other Unix Make programs also require TABs, and the Posix standard requires it as well.) Make sure that the line whose number is printed in the error message (in this case, line 10) begins with a TAB.