:-moz-ui-invalid - CSS: Cascading Style Sheets
lue becomes valid. required items have the pseudo-class applied only if the user changes them or attempts to submit an unchanged valid value. ...
...at creates a red "glow" (using the box-shadow property) around items, which have this pseudo-class applied. see the :invalid pseudo-class for an example that shows how to override the default style. the specification for :user-invalid is still in progress. ...
...ound items, which have this pseudo-class applied. see the :invalid pseudo-class for an example that shows how to override the default style. the specification for :user-invalid is still in progress. ...

UI pseudo-classes - Learn web development
ting, but as yet not well-supported in browsers: the :blank pseudo-class selects empty form controls. :empty also matches elements that have no children, like <input>, but it is more general — it also matches other empty elements like <br> and <hr>. :empty has reasonable browser support; the :blank pseudo-class's specification is not yet finished, so it not yet supported in any browser. ...
...nable browser support; the :blank pseudo-class's specification is not yet finished, so it not yet supported in any browser. the :user-invalid pseudo-class, when supported, will be similar to :invalid, but with better user experience. if the value is valid when the input receives focus, the element may match :invalid as the user enters data if the value is temporarily invalid, but will only match :user-invalid when the element loses focus. if the value was originally invalid, it will match both :invalid and :user-invalid for the whole duration of the focus. in a similar manner to :invalid, it will stop matching :user-invalid if the value does become valid. test your skills! you've reached the end of this article, but can you remember the most important information? you can find some further tests to...

Pseudo-classes - CSS: Cascading Style Sheets
html living standard living standard defines when particular selectors match html elements. selectors level 4 working draft defined :any-link, :blank, :local-link, :scope, :drop, :current, :past, :future...
...:where() specifications specification status comment fullscreen api living standard defined :fullscreen. html living standard living standard defines when particular selectors match html elements. selectors level 4 working draft defined :any-link, :blank, :local-link, :scope, :drop, :current, :past, :future, :placeholder-shown, :user-invalid, :nth-col(), :nth-last-col(), :is() and :where(). changed :empty to behave like :-moz-only-whitespace . no significant change for other pseudo-classes defined in selectors level 3 and html5 (though semantic meaning not taken over). html5 recommendation copies the relevant section from the canonical (whatwg) html spec. css basic user interface module level 3 rec...

<input>: The Input (Form Input) element - HTML: Hypertext Markup Language
ed attribute set on it. only matches elements that can be required. the attribute included on a non-requirable element will not make for a match. :optional <input>, <select>, or <textarea> element that does not have the required attribute set on it. does not match elements that can't be required. :blank <input> and <textarea> elements that currently have no value. :user-invalid similar to :invalid, but is activated on blur. matches invalid input but only after the user interaction, such as by focusing on the control, leaving the control, or attempting to submit the form containing the invalid control. examples we can style a checkbox label based on whether the checkbox is checked or not. in this example, we are styling the color and font-weight of the <label>...