PHPLint, JSLint, and I recently came across "you can lint your JS code on the fly" while reading something about some IDE.
So, what is "linting"?
Linting is the process of running a program that will analyse code for potential errors.
See lint on wikipedia:
lint was the name originally given to a particular program that flagged some suspicious and non-portable constructs (likely to be bugs) in C language source code. The term is now applied generically to tools that flag suspicious usage in software written in any computer language.