There are two flaws in this article. For simplicity, let’s call them .box, .box-rounded, .box-rounded, .box-wide, .box-rounded-wide, and so forth. You can see

There are two flaws in this article. For simplicity, let’s call them .box, .box-rounded, .box-rounded, .box-wide, .box-rounded-wide, and so forth. You can see that several of these would be required to cover all the possible box styles. And what's worse, each of them includes a lot of duplicate code. There is no reason to repeat the basic box css in this situation. Just do .a, .b, .c { basic box css here } I'd never actually use a class name like .box-rounded-wide, and I hope you wouldn't, either. It just makes for a good example. If this is a real-world situation it shouldn't be too hard to come up with a real-world example. (If it isn't, there's no reason to talk about it)