What version of CssMin are you using (source and/or build)?

3.0.1 build

What was the input stylesheet and/or configuration options?

@-moz-document url-prefix() {
  ...
}

What is the expected result?

@-moz-document url-prefix() {
  ...
}

And what is the actual result and/or error message?

@-moz-document url-prefix() {
  ...

Please provide any additional information below.

This tag allows for CSS targeted specifically at Mozilla based browsers.  
Because it isn't recognized correctly and instead strips out the closing brace, 
and other items after it fail to work.