The use of "<length>" in the properties and values syntax looks confusingly too much like an HTML tag. We don't like it, and would like to consider alternatives. Input welcome.

The "<length>" syntax is CSS meta-syntax, and there's a strong concern that it's going to be difficult to learn for web authors.

One alternative would be some kind of explicitly constructed object tree, using for example the typed OM constructors are leaves. This isn't trivial because we need to support things like the | operator (and eventually other operators too).