Came across this article discussing whether CSS is copyrightable. It is pretty interesting because CSS consists the characteristic of software codes and also expression, in a formated way. So I was not sure how we should view CSS before reading this article.
Basically it says that CSS is not copyrightable due to software restriction: “The code fragment in question must generate machine code in the executable” to be copyrightable (executable being .exe or any other executable format (examples include is Linux ‘executables’ and Mac ‘executables’) as well as executable code generated from HTML (and other languages that generate HTML code: asp, php, jsf, etc…) for the browser”
However, the whole look and feel, such as the use of color within CSS, as this together with CSS can be trademarked as trade dress and therefore be enforceable if you are competing directly or indirectly with the original creator.
More detail:
http://b0x0rz.deviantart.com/journal/Is-CSS-Copyrightable-214148624