Just in case the parent was misinterpreted: I think "inefficient" is referring not to how space-inefficient the CSS is, but that it forces the browsers to do a

Just in case the parent was misinterpreted: I think "inefficient" is referring not to how space-inefficient the CSS is, but that it forces the browsers to do a lot of extra work. (In the vein of https://developer.mozilla.org/en-US/docs/CSS/Writing_Efficient_CSS https://developer.mozilla.org/en-US/docs/CSS/Writing_Efficie... )