JSHint maintainer here.
JSHint—the version used on the website—requires you to use function-level strict mode in your code. It is very easy to turn that off, you just need to uncheck "Warn when code is not in strict mode" checkbox:
Why don't we allow global strict mode as suggested by @Czarek? Because some of the JavaScript files used on your page might not me strict mode compatible and global strict mode will break that code. To use global strict mode, there is an option called globalstrict.
Hope that helps!
