One embodiment of the present invention provides a system for facilitating compression of a Cascading Style Sheet (CSS) file. During operation, the system stores the CSS file in a local storage device and identifies a merge parameter in the CSS file. The merge parameter can be one of: a repeated selector, a repeated property in a selector, and a same value of a property in different selectors. The system then determines whether a merge condition is satisfied for the merge parameter and merges the merge parameter in the CSS file to obtain a compressed merge parameter. The merge condition indicates whether merging of the merge parameter is consistent with original style in the CSS file.