I always liked to mix both, having somewhat "semantic" classes like .message.error, but then also things like .w100 { width: 100%; } .nopad { padding:

I always liked to mix both, having somewhat "semantic" classes like .message.error, but then also things like .w100 { width: 100%; } .nopad { padding: 0; } etc. to modify the "semantic" classes where needed, in essence creating a mini-framework for every new project.