Being included in :link, :visited, :any-link?

[domenic]

This is pretty low down on the priority list for primitives, but it's worth noting that the list of which elements are considered "links" is fixed forever as a[href], area[href], link[href]. We're getting around that partially by applying our custom "UA styles" to custom-a[href], but maybe it'd be worth talking about letting these UA-defined pseudo-classes be redefined, especially once @TabAtkins's custom pseudos spec takes off.

[tabatkins]

There are a number of pseudo-classes and concepts that hook into the host language. For example:

• more elements can match :hover than just the hovered element and its ancestors - when you hover a form control, its <label> is counted as hovered too.
• a small list of elements can match :active when they're being "activated", with any method (all elements can match :active while they're being clicked).
• which elements match the :drop() pseudo-class, depending on its arguments
• all of the input pseudo-classes
• which elements match the column pseudo-classes :nth-col(), :nth-last-col(), and which are indicated when the column combinator is used from a given element.
• whether an element is "featureless" (matching none of the feature selectors, like the host element within a shadow tree)
• which values of :dir() and :lang() match the element (though we should probably leave that solely to the existing HTML mechanisms of the dir and lang attributes).