CSSO (CSS Optimizer) 是一个不同于其它的 CSS 最小化压缩工具，不仅对 CSS 做压缩还对 CSS 进行结构分析，从而相对其它压缩工具生成的文件更小。

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

项目主页：http://www.open-open.com/lib/view/home/1385370007338