Brainstorming for Selectors Level 5

Selectors 3 PR

Selectors 4 ED

numeric attribute selectors, e.g. [height>2], [count<=5], [balance<0], [#row>1]

::quote-start and ::quote-end, to match characters with the Quotation_Mark property that are direct children of the element and that are immediately inside the start and end (respectively) of the element, ignoring White_Space characters. (This would help a lot with <q> in HTML5.)

:placeholder - matches form elements displaying placeholder text. This allows web developers and theme designers to customize the appearance of placeholder text, which is a light grey color by default. This may not work well if you've changed the background color of your form fields to be a similar color, for example, so you can use this pseudo-class to change the placeholder text color.

::window pseudo-element

limited descendant combinator (more info) – foo>bar, foo>:not(bar)>bar, … comes hardly close

Better definition of ::first-letter, see also note in Selectors L3

::first-words(n), ::first-lines(n), ::nth-line(an+b), ::last-line etc.

semantic pseudo-class selectors e.g. for headings or “visible” elements (i.e. not <script> or <style>) akin to :link etc.

Clarify that first formatted line is not triggered when preceded by a block http://wiki.csswg.org/spec/css2.1#issue-268

UA hint pseudo-element selectors ::typo, ::match etc.

empty input selector

more of the user action pseudo-classes

More time pseudo-classes: :time([ before <time> | after <time> | <time> to <time> ])

only-child-parent Most use cases for the parent selector care only about the only child. This doesn't have the same perf implications as a general parent selector. – solved with :matches() and $

dynamic values selector - already handled by ::value pseudo-element in CSS3-UI.