CSS Minify Tool
Minifying CSS removes all of the spacing, indentation, newlines, and comments from your properly formatted CSS code. These elements aren't required for CSS to function correctly. It also makes reading the CSS more difficult.
Before releasing their code, many developers follow the 'best practice' of preserving a 'beautified' version and running the styles through a minification software. They'll also combine all of their style files into a single document.