CSSO (CSS Optimizer) 是一个 CSS 最小化压缩工具，不仅对 CSS 做压缩还对 CSS 进行结构分析，生成更小的文件。
安全转换：

Removal of whitespace
Removal of trailing ;
Removal of comments
Removal of invalid @charset и @import declarations
Minification of color properties
Minification of 0
Minification of multi-line strings
Minification of the font-weight property
结构优化：

Merging blocks with identical selectors
Merging blocks with identical properties
Removal of overridden properties
Removal of overridden shorthand properties
Removal of repeating selectors
Partial merging of blocks
Partial splitting of blocks
Removal of empty ruleset and at-rule
Minification of margin and padding properties
可以通过codekit使用此插件。