It's wrong because it's useless: you can use inline styles instead (and if you gzip the html it's probably going to be smaller as long as you factor in the framework, since essentially you are using numeric LZ backreferences instead of useless long class names).

The whole point of CSS classes is that they don't map to fixed styles, so they offer a useful abstraction, allowing you to change the CSS class definition once and effect all elements it applies to.