RCSSmin is a CSS minifier. The implementation is based on the semantics of the YUI compressor, but aiming for speed instead of maximum compression so that it can be used at runtime rather than during a preprocessing step. rCSSmin does syntactical compression only (removing spaces, comments, and possibly semicolons). It does not provide semantic compression (like removing empty blocks, collapsing redundant properties etc). It does, however, support various CSS hacks (by keeping them working as intended).