I didn't say it was for default configuration, just configuration. The class attribute works within this system. I, as the owner of the document, configure the

I didn't say it was for default configuration, just configuration. The class attribute works within this system. I, as the owner of the document, configure the class attribute. I can change its configuration over time, but only I do that. An alternative system would be where the browser adds and removes classes of its own, in response to things like hover/focus state. Thankfully it doesn't, and pseudo-classes are used instead.