Is cascading style sheet open source?

Cascading Style Sheets (CSS) itself is not software but a style sheet language used for describing the presentation of a document written in HTML or XML. CSS is standardized by the World Wide Web Consortium (W3C) and is freely available for anyone to use, making it effectively open in nature. Since CSS is a specification rather than a software program, it doesn't have an "open source" license like traditional software; however, its usage is open and unrestricted.