It is the code in "View Source" to which she/he refers rather than it's rendering
Fer hevvins sakes, I understood that. (Uh, didn't the remainder of my post make this clear?)
When space is lacking between attributes then the whole tag is shown in red.
Does red simply mean "This is something we don't like"?
:: back to re-check something ::
In view of their reaction to the DTD, I thought they might be highlighting only those entities that HTML 5 doesn't approve of (apparently everything but & < > ?) but nope, & looks the same as the others.